As you say, what triggered your response was the use of the phrase "I'm not a feminist" from someone who, by all accounts, seems to fully support gender equality. The issue is whether "feminist" and "feminism" means gender equality or something else.
Perhaps my use of the term "entirely" is unfair. But certainly this was a major point of your article.
You can insist on the term "feminist" or "feminism", but you will alienate people who could be your allies in a fight for gender equality. You would be insisting on a gendered term to represent the fight for gender equality. There are some people, both men and women, who cannot accept that and so long as neither side gives in, the common cause will not advance.