The irony in this post is surprising. You're making the assumption that we're making judgmental assumptions and then judging us for our assumptions.
Keep in mind that we INFJ's are even more rare than you are, as an INTJ. So assuming that there are lots of them in your classes seems unfounded. I mean, even though those are classes that we would be attracted to, for all I know, that may be increasing the percent of INFJ's present from the standard 1% to, say, 4%. Maybe I'm way off. So okay, for the sake of your argument, let's say that your classes are indeed 60% INFJ. So then, what is making you think that these people are judging you?
In college, I almost never intentionally talked to people in my classes. I mean seriously, I can't remember a single instance. Most of it was due to my self-conciousness as an INFJ. Also, a lot of people think that female engineering students can easily mooch off of their male classmates, so in trying to prove that I was not doing that, I distanced myself a lot from my classmates. Maybe they, like you, thought that it was caused by the color of their skin. I really hope not! School was also extremely stressful for me, and talking to classmates inevitably made it more stressful, because they would start asking me for help even though I had absolutely no spare time.
My point is, there are a whole lot of reasons for INFJ's to stay away from their classmates. I'm sorry that this has happened to you, and I hope that it's not actually hoards of INFJ's making negative assumptions about you. However, if they are, it may have more to do with your personality. Your post is very accusatory and a bit manipulative, with no supporting arguments. If your verbal communication follows that same style, then the people you're trying to reach out to may feel attacked or confused. I'm really not trying to be harsh here, as I'm sure you've experienced a lot of frustrating racism/culturalism that caused you to make this assumption. And that really sucks; I'm not trying to downplay how much that sucks. I'm just saying that you might be able to alter the situation a bit.