My point had nothing to do with whether the complaints are valid or whether the content should have been published without commentary.
In general, things rarely have get to the point where someone has to say "you are not welcome here" for people to not feel welcome, right? There's all kinds of subtle things, little comments, shibboleths that are or aren't used. If the standard for people proving that they are unwelcome is an explicit statement to that effect, then we will miss out on a lot.
And if we want to be empathetic and to create a welcoming environment it's incumbent on us to take people's complaints seriously. A flippant, dismissive attitude towards complaints is itself one of those subtle things.
In this context, I think it is instructive that a senior D&D designer is willing to apply the word "grognard" to people with concerns about the publication. Do all self-described grognards have that concern? Would any be upset about being conflated with people who do? Does that conflation indicate some lack of empathy for older gamers? Perhaps one could say: "I know know some people were upset about it, but I know many grognards who support the inclusion of that text".
Indicate some experience with the community. Indicate that you know its not monolithic.