That's a cheap shot! You're factually correct but it's clear that you want to suggest a subtext. The man is reported as having had psychiatric problems over a significant period of time and is said to have asked for counseling the day before the tragic attack.

I would say (wouldn't you?) that someone who said 'To persuade everyone to vote Leave, I'm going to kill a Remain supporter' is in dire need of immediate psychiatric help preferably with the help of a strait jacket.