In war, lines are drawn, and sides are picked. Percy was on the wrong side at the wrong time. After he disowned his family, he was offcially the enemy.
And from the other side? His family was the enemy.
The entire theme of the story is that not everyone is truly evil or wrong, not Percy, not Peter, not even Tom Riddle. We’re all just human, and we’re all in the wrong place at the wrong time. Why do you think Percy was redeemed? Why do you thing there was so much emphasis on Tom’s past to show he was human? Why do you think Molly Weasley used an unforgivable curse even though that was considered evil? Why do you think Remus was a docile soul even though he was housing a monster?
“The world is not divided into good and death eaters.”
Percy Weasley was in the wrong place at the wrong time, and yes he disowned his family, but they pushed him away just as hard as he struggled to break free. His own brothers joked multiple times that Mrs. Weasley shouldn’t miss him. That must have hurt, so why should he continue talking to them?
He is a grey area character, not flawless, not evil, but human, and that’s why I love him, and why people like you should step off and try to see things from his eyes for a moment.