IMO you might be overindexing on the usage of that word. It is clearer what Musk means in context. Again, he is simply saying that he won't let advertisers pressure him into changing X. That is clearly all he means by "blackmail" even if the actual usage of the term is incorrect.

He is fine, his values simply don't align with most peoples'. He is acting quite consistently with his stance on how he wants to run X (eg profit is not the primary goal.)