It's not a Remain argument WW, it's merely an argument illustrating the weakness of your 'it wouldn't happen because it wouldn't' line.
Just a brief glance at 20th c history would show you the ignorance and naivety of 'it could never happen here'.
Not that you have ever studied history, clearly.
The point you are trying to evade of course, is were there to be a successful referendum on death penalty, you would not support parliament implementing it no questions asked, nor, on current form, is it likely to.