Using "he or she" as a catch-all.
In order to be inclusive of all people, we often use the socalled gender catch-all "he or she." But when making it a goal to be inclusive of all people under the transgender umbrella, it's important to remember that binary pronouns don't include all genders.
Non-binary and transgender individuals sometimes use pronouns like they/them and ze/hir. Using "he or she" actually excludes a group that deserves to be recognized.
The solution: The limitations of our language make correcting this problem tricky. Intentionally using "they" as a term to be deliberately inclusive to all genders works well, but may irritate some grammar lovers. Another option? Just rewrite the sentence. It's worth the trouble.
(From: “5 accidentally transphobic phrases allies use − and what to say instead”, Mashable, http://mashable.com/2015/ 10/18/transgender-ally-words/#Q0K4bAJH7kqV)