I would still say "what's the big deal", but that's just me. And if someone did say that to one of the religions you mentioned but didn't say it for Christianity then I'd say they were a hypocrite.
And I get that there's a potential conflict of interest. But the thread title is 'constitutional violation' and I just don't see that. The bolded part above is hypothetical. We don't know what happened. And the article made it seem like it was completely voluntary. Besides that, what's your hard rule here? "You can't talk about religion ever if you are a coach or teacher"? Because that's not gonna fly.
You don't see a difference between a coach or teacher talking about religion in a general sense and baptizing someone to devote their life to Christ?
You think a parental reaction would be the same for:
Hey Johnny, how was school today?
Good, coach talked to us today about Mohammad and Islam.
-or-
Hey Johnny, how was school today?
Good, coach talked to us today about Mohammad and Islam. it was interesting and I really like coach so he asked for volunteers and I have now said my testimony to Islam in front of those with the faith so I am now a Muslim!
Finally, the reason it is possibly a constitutional violation IS because of the potential conflict of interest. Our forefathers wanted true freedom of religion and knew that members of government are influential. That is the point.