i'd open masquerade/- on 5/2 here, but i can see an argument for igg/-, picking up masquerade on the next shuffle. i mean obviously you are sad to be 5/2 but this doesn't change the fundamental layout of the board. if my opponent buys any igg's i'll get a second masquerade; if not i'll probably get an embassy at some point; otherwise money and green. maybe a 2nd masquerade anyway instead of the embassy? dont know.
the thing is, cursing isn't very good in the face of masquerade (exceptions: lots, but especially mountebank is still quite good). it's not just that the opponent can pass you a curse; the passing is really almost a red herring. it's that the tempo you lose cursing them (spending a 5 money turn buying a silver-) is not made up for by the tempo they lose by having a curse in the deck (masquerade being extremely fast).