Let's think about TOS in the 1960's. The civil rights movement was in full swing and we were in a Cold War with Russia, not too long before we had locked up Japanese Americans in concentration camps. With all of this is the minds of the Americans gene roddenberry created a show where an African, Russian, and Japanese man worked along side an American and an alien, who's personality is easily identifiable for people with autism. Tell me that isn't political. I wouldn't say that Star Trek is the most progressive show ever, but it has always leaned toward progressive values. So why stop now because some bigots might not like seeing a transgender on tv?
I don't want to keep going into making this a large argument, so I'll just keep it a bit more brief. The idea that TOS used different ethnicities is still different. Yes, at the time we were still not too far out from WWII, and we were in the Cold War with Russia. I think the idea was more or less to show a truth, that just because we're fighting or fought those groups, not all of them are horrible or hate us or anything like that. In the case of Uhura, she was African-American on a show during a time where Civil Rights was a big deal, and they were fighting for their rights. Kind of falls into the same premise as before in a way.
An alien identifiable with Autism, I can't be fully sure how others feel on that, but as a person who does have Asperger's Syndrome, I know I definitely identified with the logic of Spock.
That still isn't really on the same plane as pushing a political agenda through a television show, especially at a time where you're trying to get some new fans as well. Making a character transgender or anything similar is simply that. It doesn't bring in anything special, other than the usual agenda pushing. In fairness to both sides politically, and to prevent alienation of any viewers, it's just not something I'm comfortable with putting in. You do have to consider both sides in the situation, and not just solely what you want to see because you think everyone should just suck it up, and that those who disagree are "bigots".
With different races specifically for diversity, I don't have a problem with that, as long as they do well with the character. I'm not focused on some invisible quota to have a specific amount of racial diversity or any of the like, especially in a show like Star Trek where there's tons of alien races to focus on instead. In any case, I don't know about anyone else, but I don't see what the issue with (very specifically labeled) "straight white men" is.
For roles, whoever in an audition can manage to portray the character best is who gets the role. I'm not gonna run around asking for very specific races for a role, unless that role calls for it. Again, I have no problems with having some diversity, but for a main cast I'm not going to go chasing around looking for a very specific race. I get your concept of having different races for heroic characters and the such, and I think that's completely valid and fair. Just not gonna chase my tail on the matter any further.
As I was recently reminded, too, I can't please everyone. How solid the writing is, the characters are, should be the focus, not how politically correct or favoring of one side or the other it is. If you can't enjoy the series if it makes it, just because it happens to not be fully in favor of your personal or political views, then that's your loss.
Not trying to be rude or nasty, but as time has taught, if I don't have principles to stand by, then what do I have?