"Your dog stuff in my garden"
"Who cares your dog did it too!"
That's not the same thing. We don't measure candidates by absolutes - we measure them by how bad they are relative to other candidates, because we're voting on them. So imagine that you're voting between two gardens and someone says:
"Garden A has dog stuff in it."
"Yeah, but Garden B has ten times the dog stuff in it."
Which one will the judges vote for?