Oxford defines virtue as "behavior showing high moral standards." I think assertiveness only conditionally falls into this category.
First, as noted above, assertion to one can be aggression to another, thus questionable high moral standards. However, if both parties agree it's not aggressive, then is it indeed morally good to be assertive? To me, morally good is a higher bar than simply being non-aggressive.
I think if virtue is defined on moral grounds, assertiveness is not consistently enough placed into that category.
The problem is those aren't mutually exclusive and it all comes down to personal perception. An asshole thinks he is just being strong and confident, NBD! Even a kind assertive person can become aggressive after amygdala hijack during an opinionated debate. Like myself once stupidly arguing Pavarotti is a superior singer to McCartney, lol I cringe now at how impassioned and rude I became.
Others may perceive this "assertive" behavior as angry or threatening. So, even with those definitions, Jobs for instance would be considered both assertive and aggressive.
So, labeling assertiveness as good or bad morally: IMO, it's conditional.
I feel this may be an issue of semantics. To my understanding, in the NVC literature, once you start being aggressive, you are no longer being assertive - you are being aggressive. IE, they are not overlapping subsets.
This is conceptually similar to the idea of addiction. Physical dependency is one component, but the definition I'm most familiar with is that it becomes an addition (instead of use/misuse) once it has a significant negative impact on your life.
YMMV, but wanted to see if I could jump in to help clear up. It's not a comment on your definition, btw - just the context of the discussion.
I don't think the two are mutually exclusive. For example, one can express their hatred of a ethnic minority group in a strong and confident way such that people take notice, which by your definitions could qualify as assertive and aggressive.
Why are you so scared of this topic? You are trying so, so very hard to make assertive = aggressive. Maybe you should reflect a little bit on why you are trying to force a narrative so hard? Perhaps this is a touchy spot for you.
First, as noted above, assertion to one can be aggression to another, thus questionable high moral standards. However, if both parties agree it's not aggressive, then is it indeed morally good to be assertive? To me, morally good is a higher bar than simply being non-aggressive.
I think if virtue is defined on moral grounds, assertiveness is not consistently enough placed into that category.