Yes, people should be debating and arguing, even if some people will never change their minds, because debate is healthy. Debate helps people recognize other points of view and consider what other people think, even if they are set in their opinion. Discourse is healthy for humans, and it even gives them energy.
Honestly I think debating and arguing about things is a waste of everyones time. Everyone has their own mindset and opinions and to waste time arguing and trying to persuade them to change their minds gets us nowhere. Especially when it comes to topics such as abortion, religion, gay marriage and politics.