If he firmly held the belief, and did not change his mind, then he shouldn't apologise. In that case, it's legitimate to complain about his personal views where they are not compatible with his position.

How so? he was a CEO not a politician.

Half a CEO's job is being a spokesman, representing the organization, and in Mozilla's place, representing the surrounding community.

He shouldn’t apologise if he didn’t actually change his opinion – but then you can also not make the argument that he made a mistake. Mistake sort of implies that he acknowledges he made a mistake – which he doesn’t.

You can’t forgive someone if they aren’t asking for forgiveness.

Forgiveness is really about being open hearted and keeping no record of wrongs. On the cross Jesus said:

"Forgive them for they do not know what they are doing"

Jesus had the perfect right to be angry, but he wasn't. He forgave while people were mocking him and killing him. Stephen to first martyr said the same thing while he was being stoned to death.

I don't think people are advocating for him to apologize while still believing he is correct.

I think people are advocating that he reflect on his beliefs, come to a different conclusion than he's held, and then apologize for his past views.

It doesn't seem like he is going that route.

Would you change your mind on an issue like this as a result of peer pressure?

I change my mind about things all of the time.

While 'peer pressure' is seen as a negative, if you think yourself right while everyone else is wrong on an issue it is a pretty good indicator that you should check your assumptions and logic carefully.