fact (1) a 1900 chessplayer could not know computer moves, and it can not know if it's opponent using computer program. The chance of knowing it a 1900 is not better than a 1400.
the reason is you don't know what your opponent is doing. no matter you are 1900 or 1400.

fact(2) No world champion or GM will come to this site, this site is brainking.com, a correspondence online playing site.
the reason is there are no competition and prize(money), and playing correspondence chess is very time consumeing, for a world champion or Gm, time is money.

fact (3) to day, computer won all the matches vs human
the reason, time is change, now is the computer era, the machine is so fast......himan is no match to the machine.

fact (4) GM is a short form for a Grand Master in chess, not a Grand Mother or General Motor or General Manager.
the reason is, GM could be anything if you are not talking about chess.