That's not true. If 1% of all games are fixed, which is a high estimate, than you would figure that half time time the fix would be in favor of you and half the time you would get screwed by the fix, so that stuff evens out. The other 99% of the time its mano y mano, fair and square, even steven and you are either good enough or you are not. The fixes, if there are any, all even out.
The only way fixing can hurt a bettor is if he knows the fix and bets the other side anyway. Other than that, it shouldn't matter.