Some that are too assertive need anger management in the way that you are working on assertiveness. The fact that someone resorts to attack does not necessarily mean a weak argument. It just means something ticked them off and they got emotional at the expense of their argument.

There is a sweet spot somewhere between cold logic and agressive persuasion/argument. If you are seeking to improve your assertiveness, you can't do it by rationalizing away the value of emotional involvement and denying the need for assertiveness in the first place.

The tendency of some people to declare themselves the winner of the argument because the other party raises their voice an octave is a cop out.