Mackay sent some horrible messages that were released by the person he sent them too. The guy who released them, iirc was a horrible wee shite himself who did it to put him in the shit, not through some higher moral reasoning.
Mackay didn't actually hurt anyone by sending those messages, so I tend to feel a bit "he who hath not sinned" about the opprobrium coming his way.
In answer to @Dons_1988, I don't think he'll ever be allowed to move on so long as he remains in football. He could do all the campaigning and the most soul-bearing mea culpa demanded of him and it wouldn't be enough. Righteous anger is too intoxicating and getting to dump the shit we don't want to see in ourselves on other people is irresistible.