1) to start with, you used the term "cis". Don't call us that.

2) sex is not assigned at birth, it is observed.

3) the body you are born in is your body. you may feel bad about it, for instance, i wish my body were taller and less prone to storing fat, but that does not make it "wrong".

4) first lets not confuse gender and sex. sex is what you are, it is a property of your body. 99%+ of all humans have a body whose sex is unmistakable. With the remainder, it is usually possible to figure out. All of that is purely physical. gender used to be synonymous with sex, but now it just means some kind of psychological feeling. as for identity, it's a claim. most people don't claim their sex, they just recognize it. others make claims to about their sex that don't actually match reality. so yeah, gender identity exists, but that's on the claimant, not the rest of the world.

5) if i decline to accept your claim, it doesn't invalidate you. however, requiring me to deny reality is invalidating my common sense. and stop dragging innocent bystanders along, the lgb is not at all affected by this. as for the t, sorry, not going along with your fantasies doesn't make us phobic. but perhaps you are realityphobic.