Why are we not extended the same courtesy of not having to respond
Nobody has to respond.
But the flip side of that is that unless you support your assertion, nobody has to take your argument seriously.
Here's a 'me' example - a few posts above, I asserted that there is no feminism without a critique of gender.
it's possible for an opponent (someone who believes gender has nothing to do with feminism and is off limits in feminist discussion) to require me to substantiate that assertion.
I won't, because I can't be bothered right now, as I'm tired and fucked off after yet another day of heat and smoke where I live, and I didn't sleep last night because of the humidity, and I consider it self evident.
But, in response, that opponent would be entitled to say 'Well, given you can't be arsed to support your assertion, I'm paying no attention to it.'
OK.
Now run the scenario with a genderist who can't be arsed to substantiate their (many, anti-feminist) assertions. Why should feminists be arsed ?
I mean, if anyone here wants to 'convert' me to an understanding that feminism is a movement that reifies gender, and can bring their best debate behaviour to that effort, you can PM me and I promise to bring my best listening. But I'm not gonna be convinced by a series of unevidenced assertions.