"Can they really still call themselves libertarians?"

No: because Thiel, as you've well described, is trying to assume state-like powers. No libertarian even _wants_ state-like powers: even less, for anyone else to get state-like powers. A libertarian just wants to get on with his/her thang.

An interesting thing about your point is that it shows how people just "getting on with their thang" (Thiel making loads of money, which is relatively innocent) then don't know where to stop: they realise that the way to make even more money is to ally with the state and its (seemingly) infinite $-spigot. And then, whether they'd admit it or not, they are no longer libertarians but state actors.

A necessary libertarian State would exist only to _prevent_ this kind of thing. To stop individuals' pursuit of their thang from morphing into state-like behaviour.