Considering his father neglected him, his father was legitimately a tyrant who abused his power (note how easily they found allies for the rebellion), and he found out his father was performing human experiments in addition to the fact that his father did nothing when his mother was dying (who was the only person Dylan ever received any love from), it probably wasn't that hard.
i mean if its for charlize who wouldn't /lh
but on a more serious note, he didn't act like a father to him at all. considering that dylan was neglected all his life and even when his mother died, his father didn't even care nor did he go to her funeral. he even conducted experiments on living people to make them a sword... that itself doesn't even make him a human. personally, i don't respect him as a person nor do i see him one. he doesn't only deserve death, he deserves plain torture for what he did and what he's currently doing. are you seriously defending a person like him? at this point dylan most likely only sees him as someone who's brought him to this world and as someone who shares the same blood with him, not as a father (i would too)
how he coud kill his owen father for a woman ?