This is less true, slippery slope as a fallacy is having large unclear jumps chained together to make a really improbable outcome because each improbable chain

This is less true, slippery slope as a fallacy is having large unclear jumps chained together to make a really improbable outcome because each improbable chain scales off all the previous pieces. But ad hominem as an argument is only really valid when the attack against the person is highlighting conflicts of interest, which is more reason for scrutiny of the original argument than it is cause for ignoring it entirely. You should still attack the argument itself.