This barely deserves a response but I suggest you do a bit of reading about the murders and then you’ll see where your views are wrong. Completely and utterly wrong.
Both murders were carried out by lunatics, albeit of different persuasions. A white supremacist and Nazi sympathiser on one hand, and an ISIS supporting loon on the other.
You could potentially argue that the Amess murderer should have been picked up by virtue of the fact that he had been referred to the Prevent scheme, but then you’d be locking up or intensively monitoring an awful lot of people. I know that a lot of posters on here think that having three or four thousand potential terrorists on the MI5 watchlist is no big deal, but having ten or twenty thousand under surveillance isn’t really realistic. In any case the ISIS murderer had been planning to kill an MP since 2017 and his motivation related to the UK taking action against IS, which hardly relates to the more controversial areas of government policy.
Meanwhile the Jo Cox murderer had reportedly moved to killing somebody over the course of twenty years and had idolised a number of similarly infamous oddballs, not least David Copeland.
In a similar vein, I presume you believe that the government of the day was responsible for the people killed by Copeland because they allowed black, Asian and gay people to live in the UK?