:::: Actually before I go ... you said, "You won't get any tertiary source regarding what is the mainstream opinions on the existence of gravity either" 
 :::: It took me about 6 seconds to find this 2007 article stating, "Einstein's general relativity is now the mainstream theory of gravity".  In any case, you appear to err in thinking that the RS have to be recent. (Of course, this doesn't even being to address how you err in creating a false analogy between recent Communism theories and theories on gravity.)  In any case, I don't think I can anything more here ... cheers!