Don't think so, except that I have yet to see a truly "good" frat... Most of them, even the ostensibly "Christian" ones, are full of immorality, especially if they are present on any less-than-fully-trad college campus. Lots of women, lots of overconsumption of alcohol, etc. No place for anyone of any sort to be, especially a devout Catholic. Too many opportunities would exist to deny or not assert the faith, to be tempted so sins of the flesh, and all that. Remember, putting oneself voluntarily into a near occasion of sin is pretty much as bad as committing the sin itself. "Oh, I won't fornicate, I'll just drink all this beer and hang around scantily clad women who have been drinking more than I have." Right.
That being said, I suppose there are a few really "Christian" frats out there, somewhere. If these frats happen to be completely clean of immorality and all that, then...
Is every tenet of the frat in line with Catholic beliefs? You won't have to attend meetings or otherwise "entertain" on Sundays? Would joining it be a scandal to anyone? "Oh, you're in a frat... I see how you Catholics are..." If none of these or like questions apply, then it's probably alright.
