Ah yes, his house on the famous Vermont beach-side.
Even ignoring the fact that owning three houses doesn't make one a billionaire (though I suppose in this market he'd have to at least be a millionaire, but it would depend on how he got the second Vermont house), I'm not sure why you would expect socialists to not welcome a class-traitor from the bourgeoisie? Famously Engels was a nobleman after all.
How he rails against billionaires with a straight face is a mystery.
There is no discernible difference in behavior between the rightmost capitalist and the loudest American socialist.