What is it about him that makes some people hold him in high regard and not focus on those views he expressed in the letter to the Guardian?
I think it's because the British media feel guilty about him.
When he first came to public attention, it was because he was standing as an MP in Bermondsey. It was one of those classic Labour Party sleight of hand things where they ship in middle class candidates to working class safe seats and ignore the local party's views (are they still doing this?). Tatchell was thoroughly resented by the local labour party because he was foreign (antipodean), very young (27) and they felt he knew nothing about Bermondsey's community (lots of dockers and people in the supply chain around that and the docks were closing). And Tatchell had been imposed on them. When it came out that he was gay as well, homophobia was added to the list and the local party wouldn't work for him.
He was subjected to a torrent of homophobic abuse from the local and national media. After having been a Labour safe seat forever, the liberal party candidate won, ironically it was Simon Hughes who was in the closet at that time and has spoken of his guilt at having won the seat in that way in the interim.
One of the obsessions with "wrong side of history" IMO is that a lot of people in our media were homophobic in the past and feel embarrassed and ashamed of it and are determined not to be on the wrong side again. As social attitudes regarding homosexuality shifted quite quickly and the Bermondsey by-election was reassessed, I think there was a bit of a feeling that this young man whose only crime was to be gay had been monstered by the media and with all their liberal credentials, no one had really stood up for him with any real enthusiasm. I think lots of people now in charge of the media, felt guilty about how their profession had treated him.
It's why they gave him such positive coverage in the years after. I really think they felt he was really hard done by and they don't want to be unjust to him again. So they draw a discreet veil over anything too dubious.