First of all, don't start by assuming there is anything to refute - never accept the premise of an anti-communist argument without investigating whether it's actually true! Does China really have billionaires in the ranks of the party or is that just a myth that has been popularized to try and discredit the CPC in the eyes of gullible western leftists with ultra tendencies? If they do then how many and in what positions? What is the proportion of capitalists to non-capitalists in the party, and more importantly how much actual influence and power do they really have?

Do not simply accept the framing of these sorts of "gotchas", you must always dig deeper and investigate beyond the cliche phrases and surface appearances instead looking into the actual dialectical conditions that exist. Whether or not individual capitalist elements exist in the ranks of the party says nothing about the fundamental class character of the party itself. If the party was supposedly taken over by revisionist and bourgeois forces how is it that the way the Chinese state and economy are run and the results that their system produces are still so radically different from what we see in Western capitalist systems? If the same class is supposedly in power why are they not experiencing the same social and economic dynamics? If the CPC is so revisionist why has it not liberalized the country into the ground and abolished itself like the CPSU did once it was hijacked by revisionists?

And bear in mind that what happened in the USSR happened despite there technically being no capitalists whatsoever in their ruling party right up until that party voluntarily totally disempowered itself and dissolved the dictatorship of the proletariat handing the country to the enemies of the working class on a silver platter.

Clearly one must look not just at the composition (though that also matters) but at the guiding ideology and the dominant political line within the party, in addition to how the party is organized and how it governs in practice.