I know!! Every time there is an argument against him I find it weak and grasping at straws trying to demonize him (usually in order to prove that Slytherins were always portrayed as irredeemable, unsympathetic villains, and while I agree that JKR fucked up the House as a whole by, for example, not actually textually stating the thing she now says, that Slytherins returned to fight leaded by Slughorn, I don’t think it’s fair because Slughorn.Is.Not.A.Fucking.Villain). He isn’t even that problematic imo, not more than the rest of the teachers. Exhibit #1: favoritism. True, but not out of the ordinary for Hogwarts. Everyone’s fave Mcgonagall was playing favorites way more than him. Who gives a student a time turner so she could have more opportunities to take classes? Gives another one a broom and bends rules so he could play? Etc etc. The whole school system was messed up, he was so not alone in this.
Exhibit #2: cowardliness. I mean, sure, in comparison with the Conquering Heroes Gryffindors - maybe, but in a civilian, an actual fucking teacher sort of way? what could he do but hide. he didn’t break, he didn’t betray anyone, nor himself, he just hid, and then when he couldn’t hide anymore cos he understood nobody would ever leave him alone, he joined to good side. he was never on the other side. his redemption arc was overcoming his fears, and it was glorious, and people completely ignore his character development, makes me so sad.
furthermore, exhibit #3: his changed memory. well I’m sorry but this is a lot, thinking that some remark you did to a student god knows how many years ago is the reason the most evil genocidal monster can’t be killed. what a human thing to do, try to convince yourself that you didn’t say anything, that Voldemort found it out some other way (and he could’ve). so much guilt, yet, still, he came forward to Dumbledore about it, otherwise how would he even know about the first memory… Slughorn just adjusted it a little bit, to erase his own shame. i bet if Dumbledore told him: just tell me the number he said he wanted to make, Slughorn would confess. Idk, maybe Dumbledore expected to find in the real memory the whole list of items Tom Riddle had his eye set on to use, and the list of people to kill, but, I think, from Slughorn’s point of view, he believed that once a person made these horcruxes that he is indeed immortal, therefore you can only run and hide (not an unpopular idea btw), and that how many are there is irrelevant, because how would one even go about trying to find them? (and they wouldn’t, if only Tom Riddle wasn’t leaving his soul all over the Wizard History Museum).
so, overall, Slughorn: a good person, very human, caring and nice, not prejudicial against neither muggleborns, nor women, nor giants, nor anybody, a good teacher who doesn’t bully but helps his students learn, motivates them with a carrot not a stick (unlike Severus “I will kill your pet” Snape lmao), was loved universally, never did anything evil, used his cunningness and ambition to make other people see greatness in themselves and shoot for the stars, and felt only pride and never jealousy about it, also probably hilarious and great to be friends with (the dude turned into a chair hiding from Death Eaters. what a great, unorthodox mind). I had teachers like that, ones who believe in you and make you feel special, noticing your talents when the rest of the world (and your inside voice) is telling you you have nothing, and, from personal experience, it can change a person’s whole outlook on life. i bet Slughorn changed many lives. so i dunno, a great character imo, I love him. maybe this is why I associate myself so strongly with Slytherin and not other houses. I would’ve thrived under someone like Slughorn.