Because Mumsnet FWR is engaged in encouraging a culture shift of creeping homophobia, which I and my friends are directly impacted by, and people need to highlight this and show it for what it is.
Posters on this thread have minimised and defended removal of Pride flags that are used to show acceptance and welcome for gay people. They know full well that this is frightening, intimidating and hostile to young gay people in particular. And they are defending and minimising it.
Neither is this a one off. Mumsnet Feminism and Women's Rights has proven to be a welcome space for homophobia of this sort, there are many threads with similar attitudes.
This has the result of encouraging the normalisation of prejudice and unsafe environments for gay people, where we have to hide ourselves as we are being told our visibility is not acceptable and will be met with harm.
Homophobic attitudes and environments lead to increased hate crimes against gay people. It's just that simple.