The idea that monopolist, for-profit enterprises are practicing "extreme leftism" belies how far right the US is, at least economically.

I agree with you that Silicon Valley is an odd mixture of socialist ideals and unbridled capitalism. For example, we have tax dodging corporations like Apple pushing to elect people that have a stated goal of implementing massive tax-and-spend initiatives. Somehow it all makes sense in their minds. A cynical person would say that they are just siding with whatever side happens to be popular at the time in order to make more money, knowing that they will be able to avoid the effects of such policies through international tax avoidance schemes. But I think that many of these guys actually believe the things they say, which is an interesting dichotomy.

| Silicon Valley is an odd mixture of socialist ideals

There is literally nothing socialist about Silicon Valley. Government spending is not socialism and never has been.

If Silicon Valley supported nationalization, collectivization or unionization, you would have a case. But they don't, in fact they're pretty obviously against all of them.

Many in Silicon Valley advocate for things like basic income and socialized medicine. I’m not saying that these are good or bad, but they are socialist ideals.

| Many in Silicon Valley advocate for things like basic income and socialized medicine.

UBI is not socialist, it has roots in Austrian economics. Most socialists are opposed to it, although some might accept it as a short-term compromise. Like I said, socialism is nationalization, collectivization or unionization. It is not the negative income tax proposed by Hayek which maintains market relations and alienation of labor.

As for universal healthcare/single payer, can you show me people representing Silicon Valley that support Medicare For All? Not just employees, not the proles, but actual power brokers?

This is easier than you are making it. The right majority has gone off the deep end. The farthest left minority would jack up taxes substantially. The left moderate majority would increase taxes somewhat in a way that leads to long term prosperity.

Allowing the right to take the country on the crazy train to moral and economic destitution is bad for business and the furthest left are a manageable risk. The smart money is in on supporting moderate right and blue majority.

Does a private company have the power to silence a sitting President?

If so, why? I'd expect the President of the United States to have communications channels not controlled by a private company.