For one thing, I don't think "many people in this minority are mean to me" is ever a good reason to turn against the entire group. To use the old comparison again, it's not appropriate to say that you were bullied by black people, so therefore all black people should stay segregated. That excuse will never fly, and the same applies here.
Many trans people are angry at the way they are treated, and rightly so. While they may often lash out inappropriately, that doesn't mean it's right to dismiss all of them because of the angry ones.
As for those of us not part of the marginalized groups, most of us simply take a hard line stance on respecting people who can't help the way they were born. Give people basic human respect for who they are, regardless of who you think they should be. If someone suggests that trans people are predators or perverts just because they want to be treated as the gender they feel, then yes, this person will be dismissed as a bigot.
As for Joe Rogan, he has come out on the wrong side of... Many scientific issues. He's an idiot (and has admitted it occasionally), but he often forgets that, and takes strong positions that are go against the medical and scientific consensus. He's not a doctor and he doesn't have all the facts right about trans physiology, and he's said some ignorant things in that regard. He is generally hated because he mixes up his ignorance with scientific analysis, whether it's about trans issues, or about COVID, or anything else.
And I know some news articles have been happy to misrepresent some of the things he said, and that's bad. Because the people who already don't like him are more willing to believe out of context quotes. But he already says enough that is terrible at face value, and making things up doesn't help anyone.
If you want to win elections, the party has to be something people want to vote for. Right now, the only thing the Democrats have going for them is that the other side is even more unhinged. Simply being "less bad" just isn’t enough anymore.
Now you are mixing some things up. "The Left" consists of a large group of people who are not Democrats. Most of the left didn't particularly want Harris, they just understand the reality of the American two-party system. We are still critical of the Democrats because we want them to represent us more, but we support them because they are the most left viable group we have.
That said, the Democrats have a LOT more to the party and platform than "less bad than Republicans." Historically, the Democratic administrations usually created a stronger economy for the middle and lower classes, while reducing the national deficit. They have made important strides for climate action. They continue to push for health care improvements. Harris' campaign included specific issues and plans in her platform.
The trouble is that many people just ignore these things. A lot of Republicans just don't believe that democratic policies often help them.
And the less politically involved people don't even bother to read any of these things. They just see the news headlines about identity politics that are pushed by the media. These are the people who generally fall into the trap you are describing. But no amount of us bringing up the real political platform will ever be as memorable as the headlines saying that someone is mad at someone else about something.