A "meta-argument" against all future arguments for God's existence ?

[Belacqua]

In my opinion, Karl Marx was, is and will forever remain a great thinker and philosopher simply due to the fact that he advocated an end to child labor, which was prevalent in industrialized, capitalistic societies during his and Engels' lifetimes.

Seconded. (Speaking strictly for myself.) 

Maybe you've heard -- in late 18th century London a bill was proposed in Parliament that would have required buildings to put out their furnaces while the child chimney-sweeps were inside the chimneys. It was opposed by most landowners and took decades to become law. Lots of orphans got burned up but they were cheap to replace.

Having said that what Russia is doing in Ukraine is wicked, unnecessary and reckless.

I don't think modern Russia has anything to do with Marx any more.