Here are the facts:

If you believe that subjective opinions which are not based on evidence are morally acceptable, then you must believe that sexism, racism, etc. are acceptable

This does not follow. (It can be repaired by adding an "all" to the antecedent but then then the conclusion in '3' would not follow from 1 and 2.)

Is there a better way to phrase this?

Basically, no. Your argument is irredeemably flawed.