The day people stop getting so upset with double standards over what others say on stream and in vc can't come soon enough.
Though this doesn't apply as much in this case, people lurk streams to cause drama way too much, and it really shouldn't be a surprise if people talk some trash in pug vcs/scrims/matches. That's not to say that they're in the right for doing so, and I myself am guilty of talking a fair bit of trash. Regardless, it shouldn't be a thing that defines your opinion on a person. People get worked up and say things they don't necessarily mean, tend not to be as focused on social aspects or tactful wording and sentences.
I would reason that out of game/tf2 related voice interactions are much more important/meaningful and sin is handling it like a decent human being, so props to him for that.
To the transphobia matter, it's a valid concern and shouldn't just be disregarded. Raising awareness and trying to speak out against it isn't something that should be punished, the same sentiment can be applied to something such as racism. The person speaking may be in the wrong, but I don't find it fair to hold that against the concerns as a whole. I do think in this case the concern is a bit misguided.
There are much bigger offenses than someone joking about estrogen rage in a vc; such as people who go out of their way to harass people out of game for things such as their identity, who should be isolated from the rest of the community (to clarify, stuff like dms specifically with the person, or going out of their way to get other people to bother a person for their identity outside of the game. Things that'd directly lead to emotional/mental harm, not advocating for the monitoring of discord servers or anything like that; more targeted harassment that leads to more tangible harm.). This is not to say that that sort of comment is something that should be condoned or endorsed, but communities require a gradual shift in order to deviate from those sorts of harmful cultural standards. More important to focus on the figures that actively result in that sort of behavior becoming more prominent, rather than a rerun of the salem witch trials on everyone who may or may not say some unacceptable things. The inverse of this also applies though, don't bash people for trying to bring it up as a topic; bash them if they misuse it at most. It's a real thing, and it does real harm to people.
TLDR: Don't be dogmatic.
edit: I'm getting sent to the shadow zone for the latter bits that I added, GG