Although perhaps warped, Thanos did have a reason for his actions. The tragic backstory of Thanos easily gives us insight into the reasoning behind this villains motives. In the film Infinity War, he reveals that his planet Titan was destroyed due to overpopulation when he was young. He loved his planet, and thus he vowed to save other planets from falling under the same fate as his. Thanos has his reasons for the seemingly evil things that he does. His past had a massive effect on who he became, who we see in the films and the comics.
Thanos experienced childhood trauma, yes. He does what he does for a reason, yes. But just because we can empathize with him doesn't mean that he isn't a villain. His actions are unwanted, murderous, and evil. They are unforgivable.
[P1] Thanos lost his home due to overpopulation. [P2] Thanos simply wants to save others from his home's fate.