At the risk of Arguing By Dictionary, I think that part of the issue here is in the definition of the word "violence". Some dictionaries (Merriam-Webster) define violence as "the use of physical force to harm or injure". By that definition, no, deliberately misgendering someone is not "violence". Other dictionaries (Cambridge) define it as "actions or words intended to hurt people". By that definition, it is.
Regardless, I think that the greater part of the issue is intent. I would say that deliberately misgendering someone, especially after you have already been corrected, is certainly an aggressive act, and may fall under some definitions of violence. Its intent can only be to hurt, disparage or disrespect. At the very least it ignores someone's stated wishes and devalues them. I'd be okay if someone called that "violence", though I think "aggression" is probably better, as it is less likely to provoke a reaction like the OP, where "violence" is defined as inherently physical in nature.
Misgendering someone out of ignorance about their gender status, or simply making a mistake, is neither violent nor aggressive.
Sorry if this is going over ground that someone else has covered. I'm going to catch up on the rest of the thread now.