I think I should assume SpaceX isn’t doing anything sketchy, until proven otherwise.
Monopolies are bad, but it’s the government’s job to prevent monopolies not the company itself. Antitrust is a checks and balances thing, not a self restraint thing.
I don’t see why it would be impossible for other entities to achieve re-usable rockets like they have, and then spacex would have competition.
I only hope the idea of reusable boosters, or some part necessary to implement them, isn’t locked down by patent. That would be bad for the industry and for competition.
SpaceX is kicking ass now, but in the long run we’ll all suffer if SpaceX doesn’t have any competition.