He drew a circle that shut me out–
Heretic, a rebel, a thing to flout.
But Love and I had the wit to win:
We drew a circle that took him in!
Markham highlighted something that seems obvious, but everyone who claims to fight intolerance constantly seems to miss. Intolerance cannot be defeated with more intolerance, convincing people to be more tolerant of you requires being tolerant of them. The debate will not be won until you understand where the other side are coming from and recognise that they are not bad people and they have a valid perspective.
The best way to not win a debate is to start shouting “BIGOT! RACIST! SEXIST! HOMOPHOBE!” or whatever it may be, based solely on their being against a policy that you are in favour of and without actually listening to what the person is saying.
Don’t draw your own circle and shut him out the way he shut you out, draw the circle that takes him in.