Normally such threads come from people which are somewhat in the process or trying to de-mantel a democracy. So a US president saying something like that is quite worrying even if his intentions are not to undermine the US democracy.
That is exactly his intentions. He is an idiot for using Twitter in the first place. He should have been advocating for a decentralized Internet where his followers could live in a bubble catered to them.
There's bullying and there's bullying. Some Presidents have used the IRS against their opponents. If this President uses only rhetoric, then I'm fine with that. Also, pushing rule-making authority at the FCC or FTC is not over the line the way using the IRS is.