bias discount,

life is complicated,

there will always be some people who have very fixed views on certain things, regardless of the situation, regardless of the context, regardless of the changes, they always stick to the original per-determined standing, and often, a very simplified standing of either pro or against, either 100 or 0, either all or nothing, either black or white,

certainly they have their right for their standings, no doubt about that, and most often they do have their reasons too. However it's hard and frustrating sometimes to try to make an interesting exchange with such persistent types.

one of the ways to handle such people is to develop a measure of "bias discount". If you know they are very biased to one particular standing, then discount their argument accordingly, to the degree that's warranted by the particular subject.

yet, by the same token, try not to over-use such "bias discount". Don't try to override his or her arguments with what you believed about his/her motivations. That's basic the same trap, that you do the same thing as they do in potentially throwing a baby away in the bathwater, when you take a fixed approach of "whatever they say, it's nonsense".

Always exam the merits of the argument itself first. Keep cool and calm.