This is a pretty scary threat to free speech. There also appears to be a blatant conflict of interest here, considering the owner of the "certain social platform" in question hasn't left the side of the president-elect in weeks and the Attorney General of Texas is directly aligned with the same two oligarchs - Musk and Trump.
How is this anything other than using the power of the Texas State Government to run an extortion racket, designed to funnel money straight to Musk?
Corporations are allowed to choose where they want to spend their advertising budget, and if they don't want to have their ads showing between conspiracy theories and outright hate, that's allowed.