Can a rich person be anti-establishment?

By a rich person I'm guessing you mean monetarily affluent and by establishment I suspect you mean someone that is using their wealth as a platform to support a change in the status quo. If I am correct here then my reply is that any pretence they have of being anti anything is largely based on the idea that there is actually a non dynamic in the status quo.

Because what appears to be established is already so nebulous and controvery riddled one would need to first stretch the definition of both to honestly assert any such claim as being "anti"-establishment.

Whether they are "rich" or not.

Yes. And a poor person be pro-establishment, which happens much more often.

Yes