There are nice places and not nice places, and people as well. While I certainly can believe certain places in the Federation might seem like a "utopia" there are other places like Nimbus III that are pretty bad. To pretend everywhere is a wonderful place is silly, but in some areas I can accept it, just like some parts of our current world are better than others. It's when someone make a blanket statement about everywhere being wonderful and everyone being so civilized and advanced that it breaks down. I don't want to site any real world examples because I don't want to debate examples, but I wouldn't mind debating Star Trek examples. For example, Vulcan seems to be in really good shape, I doubt there are too many slums or dangerous areas because of gangs of criminals. Maybe Earth is like that, too, and Argelius. But places like Capella and Ecos, not so much.