Klingons are violent by nature. Ferengi are greedy by nature...
If you group human beings by their backgrounds and make the same kinds of broad statements about them, you're being bigoted. Same quality of thinking that Trek puts into "alien races."
And yet, through many examples in all the different ST shows, many of those alien races have had many individuals of those races express different thinking.... be that for better or worse..... many who thought outside of the box for their own personal reasons.
IMO, Trek never put that into their alien races..... they put in cultural beliefs and practices in many of their alien races.... such as in our culture and society, people are innocent until proven guilty.... yet I believe in Mexico, people are guilty until prove innocent. We believe in certain rights, where in other places in the world, they believe in different rights.
Yet to brand everybody in our society with the same brush and the same way of thinking would be ignorant..... and they show this time and time again in Star Trek.
Take O'Brien's attitude early on towards Cardassians..... when you finally got to know a few of them, you learned that they're not all the same.... sure some are typical stereo-types of that species, but there are many others that are not..... look at Garak, Damar, what's her face who Quark had a thing for and she wanted to help her "Students" who were planning to topple the military rule on their home world...... Ghemor..... the Romulans Spock was helping..... the list goes on.
How about Rom for the Ferengi.... or Nog? Heck, even Quark had many moments.
And then you have the ones who went bad in the typical good guy species..... Dr. Soran, Duras and the Duras sisters.
Let's go back a bit and focus on Tom Riker and the Maquis..... based on Stereo-Types... one would think Humans were perfect, kind, peace keepers, etc..... that we were completely loyal to Starfleet, yet if that were actually true, we wouldn't have half the bad guys we had in Star Trek.
Star Trek VI..... how many in Starfleet were willing to assassinate their own president and why would a klingon do something so dishonorable as to be a part of assassinating their own chancellor, Gorkon?
Flip it back to our reality..... does it make sense to generalize all Americans or all Canadians, Australians, Japanese, Chinese, Koreans, etc. with the same brush?
Heck, just in our western societies alone we have multiple political and sociological divides (Conservative/Liberal, etc.) yet even in those divides, there are even further divides between those.......