The headline is misleading. According to the text of the article, the law actually only bans companies that do business with the state from engaging in such boycotts. If you’re company refuses to give ad money to Musk, then you don’t get any state contracts.
I doubt the law is unconstitutional, but it is pretty stupid. Larger companies that care about their image enough to refuse to advertise on hate filled networks are also going to be the companies that provide the best services at the best prices. The state would be stuck using smaller companies that would charge them more and provide lower quality services.