I think that it's best that your boyfriend does get a feel of what your parents do think of him. If it's not a good thing, it's best that he knows so your boyfriend would understand why your parents may not be so lenient and he can try to up his game to impress your parents more. Unless your boyfriend has some sort of superiority or arrogant complex, you can talk him into understanding that your parents mean well and that maybe he does have some qualities he should improve on.
If he bursts into rage, I can understand that but then that's not a good sign. Because that would mean you'd have to choose. But when it comes down to that, I advise you to choose your parents because you can always get a new boyfriend but you can't get new parents who will love and care for you like they do. They're only doing what's best for you. Just saying...
Anyway, yeah I think that you should tell him before your parents tell him...things could get uglier that way.
