Your arguement Sir is a non starter and pulled out as a poor excuse for abolishment whenever this is brought up.
The thing is it couldn't happen unless there is intelligence and proof and the family member has either a history or interest in murder, terrorism or associated buffoonery. It's why we have a justice system, trial by jurors, defence by barrister and a whole lot of hoops to jump through. Innocent until proven guilty. If a member of my family was involved in any form of terrorism a whole file would be available for defence and prosecution and someone somewhere would be able to provide indisputable evidence of guilt. Its not execution by association or circumstantial evidence. The authorities don't just randomly arrest and execute. The British justice system might not be perfect, but it's the best we have. I have to believe in it and uphold it, defend it. Defend my country.
Btw, I'm a retired ex Soldier, I spent the best part of 30 years man and boy in The Parachute Regiment. I believe in my country, I trust my country and I have defended it, several times. I also believe in free speech, and the right of what I consider absolute buffoons to have their say.
Nothing wrong with the death penalty, I firmly believe in that too.
Pedos, rapists and terrorists straight to the top if the list. - and that Sir is my right to free speech.