Where did you get that? I've just looked at the results for England and the questions are:
Some have suggested that **leaving the European Union** might present challenges to the UK but others disagree, labelling this as Project Fear. For each of the following please tell us whether you think this would be a price worth paying or not worth paying for Brexit?
...
Violence directed towards Members of Parliament
For the option "I see it as a risk but it’s worth it to take back control", in the column for leave voters in 2016, the number is 71%, as stated in the article.
Similarly for the question:
Some have suggested that stopping Brexit and **remaining in the EU** might present challenges to the UK but others disagree. For each of the following please tell us whether you think this would be a price worth paying or not worth paying for stopping Brexit
...
Violence directed towards Members of Parliament
For the option "I see it as a risk but it’s worth it to remain in the EU" in the column for remain voters in 2016, the number is 58%, as stated in the article.
I suspect this is being misinterpreted.
I don't think it means that violence against MPs is a price worth paying - I think if you look at the wording it is that the 'risk' of violence is a price worth paying. So that doesn't mean there would be violence, but that there is a risk of it. So people answering:
'I see it as a risk but it’s worth it to take back control'
May be thinking it is a risk, but a vanishingly small one and not something we should concern ourselves with - there is no other option that allows them to voice that opinion as the other options are:
'I want this to happen regardless of Brexit' - horrifyingly supported by 7% of people and
'Leaving the EU is not worth the risk of this happening'
So what do you answer if you don't think there is a risk of violence or that the risk is tiny - well, if you are a leaver probably 'I see it as a risk but it’s worth it to take back control'.
Frankly I think the questions are poor as they don't talk account of the believability of the claim amongst those answering the survey.