What To Do?

Ok, so this is me venting about dumb friends.. so last night I didn't have any plans so Dustin was gonna come over for open-dorm and just hang out. Then as I get off the phone with him, my roommate (who shall remain nameless) tells me that the whole gang of us are going to the diner. So I'm like 'oh that would be fun!' and she's like, 'well Justin said he's not going if Dustin goes, so Dustin can't go.' Upset doesn't even cover the emotions that flew through my veins! Justin is my very good guy friend and we hang out all the time, he doesn't get along with Dustin at all, but for my sake he's civil at least. But now he's saying that I can come but only if I don't bring Dustin? that's not cool. and then to top it all off I found out that a number of my 'friends' (are the quotes too mean?) condoned this behavior and agreed that he shouldn't be able to come. it upsets me because
A) no one seems to notice that it could bother me, they all seem to think that it is totally normal to put stipulations on the context of our time together.
B) I want Dustin to hang out with my friends and get to know them better, he already knows them (he went to Fl. over spring break last year with a number of them) but I want to hang out with the people I love together.
So I dont know what to do, should I say something to Justin, or my roommate or the other 'friends' who are totally ok with it all? or is that just gonna make it worse? I am in a rock and a hard place, I mean what I want is not that demanding. Being able to hang out with my friends and Dustin at the same time. Is that too much to ask?