Why are certain groups of people so violent?

Do you realize what you just said?

"On the cops shows it's always gangster black guys/drunk rednecks or druggie Mexicans...And at school when there are fights it is always between black guys or gang member mexicans or anger white guys..."

Who else would you expect to see on cop shows? Law abiding citizens? You see GANGSTER black guys on cops shows because they're GANGSTERS! You see REDNECKS because they get drunk and become violent! You see DRUGGIE Mexicans because the Mexicans with an ounce of dignity are probably at home, shaking their heads at this madness just like you are! This phenomenon known as lack of common sense has nothing to do with race.

Those groups you just mentioned ARE violent, and ignorant, and foolish. Just remember, the NORMAL whites, and NORMAL blacks, NORMAL Latinos and NORMAL Asians all agree with you. Those guys you saw on those cop shows ARE idiots...

My English standard is poor so I would like to share in traditional Chinese. Hope you don’t mind.

不和是從討厭而來；紛争是從憎惡而來；暴力的發動是從敵對而來。

討厭是從不同而來；憎惡是從反感而來；敵對是從傷害而來。

要作出化解，是要有策略：第一是要保持理性，第二是要有包容的胸，
第三是要克制，就是忍耐，第四就是要精神，不精神的狀態容易受剌激，
第五是要有平和，第六是不具侵略性，第七是要安全，第八是要互相尊重，
這八樣寶物，就是聰明人所有的，誰是聰明人，就是世界的守護者。

知識傳流、互相建立，打破國與國的疆界。

It's not being racist when your question includes blacks, whites, and mexicans. I think the better question might be why are men so aggressive and violent. It can be nature or it can be the culture they live in. Poverty and oppression play an important role too. Unfortunately your question is so complex it doesn't have a simple answer.

well its not necessarily just some groups that are more violent than others. but you are made to believe that some groups are more violent because of the media showing this.

How people socialize and interact within their environment is learned behavior.
Did you ever hear of "Birds of a feather?".
I don't think you are being racist. You do see that these things are more violent
in groups that are in poverty or do not live in an environment were social mores
mean much. They live up to their own expectations, not society's.
Your non-violent groups have more appropriate methods of problem solving.

Its ingrained in human nature.