It's not about being obsessive about transsexuals. It's about focussing on women and pushing back against attempts to erase women as a class which would render Feminism void as a means of analysis and therefore a tool to shine light on existing oppression and inequality. And therefore harm women in the process.
That there are barely any feminist spaces left (irl or online) that are not riven with transangst is a travesty and will (has) contribute(d) to a backsliding of thought, discussion and action that is harmful to women. Just wait until the right wingers turn their attention to reproductive rights in this country.