It's not so much about offending someone (and yes, people absolutely do sometimes get aggressively upset about it) and more about attempting to change my own mental habits. I believe like race, sexual orientation, and politics, gender is a personal topic that doesn't really need to enter into a casual, never to be repeated interaction between two people. You don't say "excuse me, old person," based on your perceptions of another's appearance. Why is gender any different? It certainly isn't an objective concept or one that can be readily or factually assumed. It's outmoded and unnecessary.

Also, as I commented earlier, if I am using what I mean to be a term of respect to make someone else feel confident and comfortable, and through my language I risk doing the opposite, why would I want to do that if it's something I can personally change?