Short Answer: YES - his buddy is more important. Your parents are complete strangers. The only reason he has to meet them is to shut you up.
Whoah, easy there. :) They're not Complete strangers, no. They're the parents of your girlfriend, so, they're people you know about to some degree, but haven't met yet. I don't think it's to shut the gal up. He even said he'd like to get along well with her parents if things progressed -- so no, that's incorrect. But it Would be to shut the other person up if they are wanting to do so in an unideal time or setting for oneself -- but the gal puts him in more than unideal but very untimely. If this was the 3rd or 4th situation where it's like that, yeah, it would be to "shut her up". I think the BF is in the right to say "No, not on that day," when he already has plans. Any disappointment by her parents is her fault for scheduling it without consulting him first.
Why can't your parents come over and watch Star Trek? Do they hate sci-fi? Do they hate TV? Are they not able to travel? Do you NOT have Skype, Facetime, or a TELEPHONE?
I don't think it's at all about that... I don't think either party would want a 1st time meet like that. They could meet in a casual setting (like BW3 watching football that he'd aim for), but from the sounds of it, she wants a semi-formal "meet the parents" situation... and knowing that, neither party would want it kicked off in a Star Trek or College Football Watching setting. Bottom line: It's kind of like going out on a formal Date to places she likes. It's good to do -- but she can't expect for him to place it on days where he always has some things in motion. She thinks her having to cooperate is rude on his part.