My heartfelt sympathy goes out to Jo Cox's family.
The whole point of democracy is that we are each entitled to our own opinion. Disagreeing with someone else's viewpoint does not give anyone the right to kill them.
It makes no difference whether you're in the Remain camp or the Brexit camp. Everyone's decision is based on things that are important to them and no-one has the right to tell anyone else how they should or shouldn't feel about any of it. People are allowed to be passionate and express their thoughts, that doesn't mean everyone will agree with them, and they wouldn't be expected to, but we live in a democratic country and we all have the right to express our views. We are all allowed to make our own decision, vote accordingly and be safe doing so.
That's what democracy is all about.