I don't think it's right for a university professor to teach without a PHD?

The requirement to teach in a college or university is a master's degree. It always has been. The PhD is needed to do academic research which is rarely done standing in front of a classroom. The PhD is usually, though not always, required to teach graduate level courses and most universities prefer a PhD for their undergraduate upper-level courses. An exception is the terminal master's degree (MFA) which is considered equal to the PhD in those fields and the professional degree (JD, MD, etc) for courses in the professions.

The professor with a PhD has a very specialized subject knowledge that is far deeper than what an undergraduate class will usually be covering. While they almost always also have a master's degree in their subject - it's their specialized knowledge that makes them most valuable.

So, if you're in a history class called "Colonial American History in Jamestowne Colony" then a PhD is what you need teaching it. But, if you're in a history class called "Western Civilization I - before 1620" then any MA in History has that knowledge and can share it with you.

Mostly though - it's a matter of highest and best use of personnel resources. People with a PhD in Literature simply don't usually want to teach freshman English classes and their time can be better used teaching other things. The instructor with an MA in Literature usually thinks freshman English class is some cool stuff. Then again, often, even the grad assistants don't want to teach freshman English but they're ideally suited as a personnel resource for that class assignment.

The PhD is not always the highest degree -- for some professions the Master's is the terminal degree. Some universities may not have the money or prestige to hire anyone with a PhD, so they go for people with a Master's degree instead. There is no reason why someone with a Master's couldn't lead most intro-level classes in any particular program. And honestly, do you know anything about the process of getting a Master's? I really don't think a PhD in the field gives a person that much of a different perspective than just having a Master's.

Having a PhD is not indicative of knowledge. For instance, if you were taking a class in designing computer operative systems, wouldn't Bill Gates be a great choice for professor? There used to be a poetry professor at Berkley who did not have any college degrees. She did have hundreds (maybe thousands) of published poems and was self taught. Issac Newton did not have a PhD and would not (using a PhD as a basis) be qualified to teach math or physics. He could not teach calculus even though he is one of the two men who invented it. A PhD is a research degree (not a teaching degree). Many colleges do not stress research in which case they often do not require PhDs. I teach at a community college (MBA) and we stress business experience to teach business (as well as a masters degree). I would rather take a course from a person who had actual experience, than one who just earned a PhD. (PhDs often get experience by consulting, but they don't start that way)

call them 'professor' except they precise otherwise. they're nonetheless a professor, even and not using a PhD. Mr/Ms is demeaning, as is addressing them by using their first call considering that they're of a greater robust rank in the college equipment.