The Republicans would be exposing the thinking that has resulted in them losing almost every culture war battle in the last ... I don't know how long. The bureaucracies enforcing anti-trust will lean left. Eventually there will be a bias of anti-trust action used to break up any companies that look to be helping Republican candidate elected. It'll be these Donald Trump court cases all over again.
What actually works for the right is free markets. Turns out if they just leave YouTube alone they get Rumble. If they ignore Twitter they get X. If Amazon makes a habit of booting right-wing sites, there will be a right wing version of Amazon. There are more than enough right wing media consumers for a free market to reward right-leaning content. Anti-trust will eventually lead to overregulation and lock in of companies hostile to the right in general and republicans in particular.
There is a much better argument for anti-trust to try and defuse the risk of a vast an hasty flash-mob forming and doing something stupid, but as a political response it just isn't going to be effective.