Opposition to the person and gospel of Jesus unites even the strongest enemies at times. Now the Pharisees were fundamentally legalists. Legalism disallows what is not wrong, and it allows what is not right. It teaches the laws of men as if they were the laws of God. It creates fear instead of love.
Legalism likes to major on the negatives.
What it does best is tell you what you CAN'T do. But Jesus tells us that keeping the law is really about what you CAN do. The Pharisees tended to major on the first. Love the Lord your God. Why by keeping his laws of course.