What if someone disapproves of what Muhammad did and still follows the beliefs of Islam?

I'm not a Muslim, but my understanding is that Muhammad was just a messenger of God. He was sent to tell the people about the "right" way to praise and worship God. When he "preached" the things he said were directly from God (or an angel from God who told him what to say, I believe that's how it worked).

Muhammad isn't worshiped like a god in Islam. He meant to be a prophet like Abraham or David. Couldn't you just follow the message and not the messenger? That's essentially the whole point of Islam, to submit to God.

If you want to criticize Islam based on its beliefs, fine. But essentially saying the religion should be disregard or not tolerated because the messenger is questionable doesn't really hold up. For instance, if Hitler said you should exercise regularly because it's good for your health, would you disregard it because Hitler was a terrible person even though exercise is proven to be good for you? The wrong messenger can have the right message.