Why do right-wing USA people consider 'liberal' and 'socialist' as derogative words?

Nothing is wrong with it. But most Democrats today are either liberals or democratic socialists and comparing USA liberals to Venezuela is like comparing apples to rubber tires.

(Dems are not this) Socialism – An economic system characterized by social ownership of the means of production and co-operative management of the economy. The State controls the means of production and provides certain goods and services to the public. There is private ownership of money and property, but taxes are generally high.

Democratic Socialism - Social and economic decisions should be made by those whom they most affect. Democratic socialists favor as much decentralization as possible. While the large concentrations of capital in industries such as energy and steel may necessitate some form of state ownership, many consumer-goods industries might be best run as cooperatives. Democratic socialists have long rejected the belief that the whole economy should be centrally planned. While they believe that democratic planning can shape major social investments like mass transit, housing, and energy, market mechanisms are needed to determine the demand for many consumer goods. Any change in government and society should be through fair elections. Many northern European countries enjoy tremendous prosperity and relative economic equality thanks to the policies pursued by social democratic parties, including Finland, Norway, Denmark, and Sweden.

Forbes rated the Best Countries for Business in 2016:
Sweden (democratic socialist)
New Zealand (democratic socialist)
Hong Kong (more capitalist)
Ireland (mixed)
United Kingdom (capitalist with strong democratic socialist tendencies)
Denmark (democratic socialist)
Netherlands (mixed)
Finland (democratic socialist)
Norway (democratic socialist)
Canada (capitalist with strong democratic socialist tendencies)
https://www.forbes.com/best-countries-for-business/list/#tab:overall

Democratic socialist countries are business-friendly. Most of their businesses, particularly mid-sized and small businesses, are doing better than ours.

See also:

Which are the world's happiest countries?
http://www.cnn.com/travel/article/worlds-happiest-countries-united-nations-2017/index.html
Norway (democratic socialist)
Denmark (democratic socialist)
Iceland (democratic socialist)
Switzerland (capitalist with strong democratic socialist tendencies)
Finland (democratic socialist)
Netherlands (democratic socialist)
Canada (capitalist with strong democratic socialist tendencies)
New Zealand (democratic socialist)
Australia (capitalist with strong democratic socialist tendencies)
Sweden (democratic socialist)

Human Development Index
https://en.wikipedia.org/wiki/Human_Development_Index

10 Reasons Why Denmark’s ‘Democratic Socialism’ Is Much Better Than America’s Crony Capitalism
http://anonhq.com/10-reasons-why-denmarks-democratic-socialism-is-much-better-than-americas-crony-capitalism/


Forbes rates the Best Countries for Business in 2015:
Denmark (democratic socialist)
New Zealand (free market with strong democratic socialist tendencies)
Norway (democratic socialist)
Ireland (mix of capitalism and socialism)
Sweden (democratic socialist)
Finland (democratic socialist)
Canada (mix of capitalism and socialism)
Singapore (mix of capitalism and socialism)
Netherlands (mix of capitalism and socialism)
United States (mix of capitalism and socialism)
http://www.forbes.com/sites/kurtbadenhausen/2015/12/16/the-best-countries-for-business-2015/#270ec47d7364

FDR, a democratic socialist, gave us Social Security, labor union laws that protect workers, and the minimum wage. As a result, the country prospered greatly. These laws, known as The New Deal, gave us the middle class, and as the Republicans destroy these laws our middle class is disappearing.

Right-wing media conditioning. The information outlets right-wing USA people rely upon continuously talk negatively about liberals and socialists to point where right-wing USA people see "liberal" and "socialist" as pejoratives.

They are told what to believe

Right wing media propaganda tells them that, and they believe it. They equate socialist with communism which or course is wrong. Many think Hitler was socialist which or course is wrong. It's nuts.

Because they're stupid and believe whatever their loudmouth wealthy overlords tell them to believe.

It's mostly brainwashing from the rich elite who own the media. There was a time when Communism may have been a fascist, totalitarian regime, however it was imposed by force simply to share the wealth of the rich with the poor simply so they could eat, because they were starving. We would hope that African countries would have the care for their fellow man to do the same when they have a huge famine and have starving children by the million, but unfortunately, they have the same capitalist greed that the US do, or particularly the right wing rich elite, or those brainwashed by them. To me, the left side is the good side, the caring, selfless, charitable side, of course if you were a billionaire, you might not see it that way, or you would, but you wouldn't care about feeding and housing people, you'd want to keep your massive wealth that you acquired through generations of genocide, murder, crime and fraud.

Mao Zedong killed 70 million people
Joseph Stalin killed 20 million

Socialism is communism light

Americans have the misguided belief that any mention of Socialism means Communist dictatorship, of the kind endured by Stalinist Russia and Maoist China. But they fail to understand that dictatorship and ideology are two entirely different things. Take for example General Galtieri of Argentina, and General Pinochet of Chile. Both of these leaders were right wing, yet were also responsible for disappearances, murders and economic collapse. Adolph Hitler was not a Socialist, not by a million miles. He was a Fascist dictator, like his friend Mussolini. The name of Hitler's party was National Socialist Party, but it was as far removed from Socialism as North Korea is from Democracy, despite having the word Democratic in it's title. Conservatives in America have been so brainwashed over the decades since before WWII that they fail to understand any concept other than Capitalism, which has caused more grief, heartache, broken families, suicides and murders than moist would ever conceive. Debt, greed and selfish interest have prevailed in America since the days of slavery. Slave/Bounty hunters were filled with greed, and chased escaping slaves in the South for the monetary reward, ignoring the desperate plight and desperate hardship of the slaves being pursued. The name "Liberal" and "Socialist" are a derogatory term that those on the right believe are terms of ridicule and resentment. But as times change, those terms become more of a badge of honor rather than an insult.

Yes, I'm sure that the socialists in Venezuela are great people and care for each other. And let's not forget about the Soviet Union. I'm guessing that Stalin was very caring, right?