That sexuality is complicated is an empirical fact.  Most people are heterosexual, but a significant minority are gay.  And now we have become aware that, for whatever reasons, gender identity doesn’t always align with a person’s biological sex.  Why is that?  I don’t think we really know. Intriguing work is being done, but the science looks to be far from settled. 

Now, I don’t think we need to wait until the science is settled to teach children the empirical facts that some people are gay and some people identify as transgendered.  And I don’t think we need to wait until science sorts out the complicated causality of sexual diversity to impart to children the value of tolerance in the face of that diversity.  That is not a “left wing” war on science because whatever the science eventually tells us, it will not justify intolerant behaviour.  We don’t need science to give us reasons to treat people who are different as human beings.