When you make it okay to be gay, it also makes it easier for straight people to deal with any same sex feelings they might have because they know it is normal too. There's less pressure and anxiety.
When you make it okay to be trans, it also makes it easier for cis people to deal with any gender non-conforming physical features they might have, because they know it doesn't define them. (For example about 10% of cis women at some point experience beard growth, baldness, deeper voices etc due to PCOS. This is a cis woman: https://www.bbc.co.uk/news/uk-england-beds-bucks-herts-63073375)
LGBTQIA+ rights are liberating for everyone, they free us all.