Of course there's a difference in your example: we're not talking loyalty of coaches, we're discussing player loyalty. To play against your former teammates means you invested nothing in them, emotionally. Remember, GS, this is brutal contact sport, not badminton. And these aren't NFL players, these are guys that play for other reasons, often for no more than to be part of something greater than themselves--- isn't that why you and I and countless others prefer it to the NFL corporate game? 
As far as Taggart's past: I'll grant him a lot of freedom here (I searched and couldn't find any dirt about him; link if you know of a story); it's what he does here that counts with me. I don't know or care to research his former actions, as long as they weren't like Altman's arguing that he didn't know a kid under investigation for sexual assault was in such trouble before Altman brought him onto the team.