If this is their rationale they should say so, so they can fade into obscurity as soon as possible and leave room for sensible people.
And how does picking and choosing which social media platforms they blast content onto fight fascism? Are Tiktok and Facebook leadership known for their antifascist stances?
Encouraging people to use X drives money into the hands of fascists.
Cross posting content isn't really encouraging people to use it.
If they want to make some principled stand against toxic social media, then have at it. This is pure pandering to a very specific group.
Twitter, before Elon, was the company that literally banned your account for sharing the hunter Biden laptop story. That story was purported to be a "conspiracy theory" but was actually true. And people were locked out of their account for sharing it. That is true fascism.