Mac doesn't hate uncle Donald. It's more like Mac literally can't comprehend him. Mac can't perceive someone who could genuinely offer him support/understanding no strings attached. It's like how Dennis and Dee couldn't comprehend Bruce Mathis. They didn't understand Bruce just wanted to help people and help them. The gang in general don't see outsiders that well. They especially can't comprehend people who can offer them help. I've seen people say that Mac hates uncle Donald and I don't think so because hate would require a level of understanding of his own issues and of what uncle Donald was offering and who he is and Mac doesn't have that. Yes ofc Mac hates himself and he's put off when he sees himself mirrored in others (it's why he doesn't like Dee's desperation for approval because it reminds him of himself even if he won't admit it) but Mac doesn't comprehend uncle Donald. That's why Charlie was so pissed. Mac has everything he's ever wanted and he doesn't seem to notice or care.
