When unkosher food gets mixed up w/ kosher food מין בשאינו מינו, it is not enough to have רוב kosher b/c טעם כעיקר and so we need ששים against the forbidden טעם.
Why don't we say that since there is a רוב kosher, the forbidden טעם is considered kosher טעם and we wouldn't need ששים?