I don't think Angel was right. Like, at all.
While it was immensely stupid of Wesley to collaborate with Holtz instead of confiding with the other guys, I'm absolutely backing his decision of taking Connor away without consulting Angel about it. With the data at hand, that's the best decision to make. It's doing the right thing for the right reason - just with very bad judgment on whom to ask for help in executing it, and this choice of help leading to disaster. And it's not like Wesley didn't pay enough of a price for his mistake; the man got his throat slit, for goodness sake!
Honestly, the first time I saw Angel trying to smother Wes with the pillow, I couldn't help but side with Holtz in the opinion of "soul or not, who cares - that guy is a monster" (especially with Angel making it clear that he's NOT Angelus at that time). I wouldn't have minded anyone staking one more vampire then and there. I have more of an issue with anyone trusting Angel ever again after this ep, not Wes. Wes earned mistrust for lack of cueing anyone else in the team in on his plan, I grant that immediately, but the way everyone treated him was considerably too harsh (Fred possibly excepted, she did seem to be avoiding him mostly because of group pressure), while everyone was way, WAY too light on Angel - who IMO justly deserved a timeout in the wet corner over that summer to think about behaving.
I grant that maybe my opinion is influenced by the fact that I am not and will never be a parent... but honestly, if being a parent would make me see Angel's behavior there as acceptable, that would be one humongous reason for me thanking God I'll never be one. Heck, I'd go so far to back him up on "I never want to see or speak to that man again"... but "I'm going to kill you now, and btw: I'm the good guy"? No, fangster, you are most definitely not.
I also fully agree with WA and PV about Angel being a master of dishing out lone decisions over other people's heads, but a sucker when it comes to be at the receiving end of it.