The crux of it is is in this part:
We feel it's the right thing to do to facilitate that debate (whilst ensuring it remains respectful) even though some would wish to censor it.
Facilitate debate - yes, MN does that.
Some wish to censor it - also true
“whilst ensuring it remains respectful”
This is where it falls down.
The tone of threads on any topic around trans people is consistently and persistently hostile and prejudiced towards trans people in general. FWR as a board is hostile and prejudiced towards anyone who posts in defence of or arguing from the point of view of trans people.
For an example, see the recent thread in AIBU in which a trans person who the OP said was talking too much about trans issues at work was disparaged, misgendered, and personally insulted numerous times.
Yes, many of the individual posts that explicitly contravened TGs were deleted, but the thread as a it still stands cannot be described truthfully as respectful towards trans people.
This is the sort of thing brands want to distance themselves from.
Then there’s FWR, where recurring themes include threads with hundreds of posts supporting a view that a trans person asking someone to use their preferred pronouns is equivalent to administering a date rape drug.
Or thread full of posters adamant that they will never ever use preferred pronouns for trans people because of some bad things that some trans people have done, and accusing MNHQ of abusive behaviours by expecting posters to adhere to the TGs on that point.