Because context is everything.
At what point is describing a violent event understood as an incitement to that event ?
It pains me to move towards BoJos side of the aisle but I personally do not read the text as urging others to actually carry them out. And I would say the same in a jury room.
You could say it's not a very well thought out or conveyed point of view, but no more.
(With the usual caveat I can only speak to facts in view).
Also the more hysterical Brexiteers become, the more they demonstrate what a shit idea it was.