Sometimes opponents in argument, especially opponents who adhere to some ideology or other, will deliberately blind themselves to your good faith. If someone says something like the following to you, either because they've learned of an affiliation you have (or are accused of having), or after you have tried to earnestly engage with them: "Your hatred has become such a large part of you that it is now part of your identity. Appeals to reason and kindness will have no effect on you. There is nothing you can do to make me forget your true intentions."
It's no longer of use to you, or to your position, to continue to be friendly and forgiving with this person. What this cold, robotic and self-righteous projection really means:"Hatred has become such a large part of how I view you that it is now part of the identity I ascribe to you. Your appeals to reason and kindness will have no effect on me, because the identity that I have ascribed to you precludes me interpreting your reasonableness and kindness as such. There is nothing you can do to erase my villification of you."
Such a person has revoked all willingness to grant you the benefit of the doubt. You may as well do the same, as all benefit you extend to the person will be taken advantage of, turned around and weaponized against you. This is why you should never apologize to an ideologue on a moral crusade if you intend to remain a free and independent agent. Zealots who smell weakness will not be satisfied until opponents are either destroyed or assimilated into the horde. This is especially true of the current climate's "Social Justice" Marxists, as their ideology denies the existence of altruism (when convenient), viewing all human interaction instead as purely a matter of power and authority. In other words, any compassion you extend is perceived by a Social Marxist as a power vacuum to take advantage of, which they will do if you fail to be sufficiently assertive.
Once you've realized you've been pigeonholed in such a way, it's about time to either back out of the conversation entirely, enact perfect robotic patience and deal exclusively in the facts, or lay the rhetorical smackdown. If you choose the latter, forget politeness. Mock and ridicule the person's unreasonable claims and standards. Get a bit mean. Bruise the opponent's ego. Reveal your disgust and disdain.
In other words, abandon the high ground in favor of the equal ground, and beat them there. You will win because you're free.
I felt like writing about this because of this hilarious clip: Middle-aged Man Triggered by MILO Poster at UC Berkeley
The guys who were confronted by the man who tore their poster down didn't apologize or sympathize, didn't try to reason with him much and didn't get aggressive with him either. They just plain wouldn't take his shit and showed him that they found him ridiculous. They took the equal ground and laughed at him, and he downright shorted out