Unfortunately I think what this encourages is being less genuine.. hiding your personal feelings when they go against the current tide. Was the problem truly that he felt this way, or that he publicly+financially felt that way? If there was no public record of his position, there'd be no controversy.
I completely disagree with his position, but I don't think shutting him up or vilifying him is the answer.
The problem is that it ceased to be his personal opinion when he donated money to and voted to strip other people of their rights (while keeping those rights for himself) under force of law. He directly contributed to preventing some of his very own employees from being able to marry in their home state of California. A right they had previously enjoyed.
If he held to his own beliefs, but allowed others to have their own beliefs and live their lives how they wanted, I sincerely doubt this would have been such a big issue.
I completely disagree with his position, but I don't think shutting him up or vilifying him is the answer.