I dont play the Grobs attack actually (ive tried it a few times with poor results), but i play any other kinds of unsound openings, like the Latvian, the Englund or the BDG.
Iam tired of self-defending me, why i play these crap.
Is a chess opening such a dogmatic thing, that only allows to play high-fashioned standard openings.
On amateur level, as 99% of us play, you can play nearly every opening, if you know the concepts and tactics.
Playing the Berlin Defence in Ruy Lopez or the Latvian Gambit with a rating of 1400 to 1800 makes no difference.
Only a good opening doesnt make you a good chess player...
However this is not to say I would ever play in a serious game, at least over the board.
This is the key statement :).
As for the WC, "slips" are relative. The slip you mentioned is at a play level that 99.99% of Grob players will never see.