As a trans-woman (post-everything, married, successful, happy), it is a mental disorder. The stigma of mental disorder is a completely separate issue, but GID /GD is still a mental disorder.
And as a trans person, you're still not immune to being intolerant of others.

It's a disorder if it disrupts your life. Problem is, you have other people artificially giving trans people a hard time, and then when they react to it (because who wouldn't react to being mistreated?), those other people are like "see, you're disordered!" and that... doesn't really count.

If it was a disorder for you and you fully accept that fact, great. You do not get to decide that for everyone else.