He was opposed to it as a private citizen, not as Mozilla CEO. His beliefs and supported causes as the former are nobody else's concern; had he been discriminating in terms of employment or otherwise making public statements it would be a different story. Or are we now witch hunting people for wrongthink?
I don't think it's "witch hunting people for wrongthink" to suggest that those in a position of power are able to use that power to influence public opinion.
Especially when that position of power is the CEO of a browser that replaces content on web pages.
Mozilla went hardcore political and Chrome copycat long after his time. There was no such controversy there under Eich, and even now as Brave's CEO he isn't doing anything to 'influence public opinion'. Browser CEOs aren't newspaper editors or activists, Mitchell Baker excepted.