When do I give up?

 After I decide not to react to the old lady who said "It's because of all the foreigners in the country, making it hard for white people to get jobs", I have been thinking about when to keep quiet and when to fight my corner. Recent Facebook discussions with Kamila's brother-in-law, about human-rights/religion, have always tailed off with resolution. I feel that I have been coming out on top, mostly because he is unable to sufficiently defend his views and descends in to him spouting clichés and insults. As with all arguments/discussions, I find it frustrating that people are unable or unwilling to change their viewpoint in the face of any amount of evidence, logic or reasoning.

 I see the subjects I tackle as ones which have complicated, but correct, answers. The issue arises when the other party, as they inevitably do, refuses to change their view. How far should I push it? I feel that I should always stand up for the truth and tell people when I think they're wrong. As recent arguments have shown, they are wrong through religious indoctrination and lack of facts. What if someone eventually listens? I think it's worth upsetting a few people if they're in the wrong. Even if I can't change them, shouldn't they still be told they are wrong? These are not taste-based, 'which band is best' debates, they are fact-based 'unicorns exist' debates. While I can't prove empirically that unicorns don't exist, we can see that they were created as fiction and there is no evidence to show otherwise.

 The most recent example would be the enforcement of sex education, which was labelled as totalitarian, indoctrination and propaganda. Here is the original article which prompted the discussion, a google translate should be enough to understand the story. I see this as one of those fact vs. faith issues, rather than one of opinion. A lot of people have the opinion that sex education for young people is damaging, but studies have shown that it lowers teen pregnancy, lowers STD cases and produces healthier sex lives once those children mature.This article is the latest to give good results, it also is a good demonstration of the scientific method setting the boundaries; we don't need to take sex education too far, because we can't see any benefits. As I said before, this wasn't much of a discussion, as the other party refused to address any of these points and resorted to comparing atheists to Hitler, again. Do I leave it alone once he stops answering? I assume he thinks he's won, all scientific evidence that contradicts him is politically motived and therefore not fact. Could forcing him to address these issues with me make a difference? Could he realise that he is wrong? I've heard Ray Comfort be repeatedly berated and educated on evolution, but he is still unable to grasp the concept.

 Have movies lied to me again? Can people really not see the error of their ways and become 'enlightened'? Would it help if I was Jennifer Aniston?