I admit I had never heard of Blue Lives Matter and had to look it up. It is a bit rich that people who have killed 'in the line of duty' without prejudice to their careers should suddenly make part of their job description a special cause. Are marines who join up told 'this job may endanger your life'? As if they didn't know?
As for the 'criticism of the FBI', it is surely a sign that there is a potential crisis of government when the President and his supporters not only brand senior officers of the FBI with decades of service fighting crime (and successfully too in many cases) as 'leakers and liars' but even set up a web-page called 'Lyin' Comey'. And when you realise this has nothing to do with the USA or the FBI but the personality of one man (no, not Comey), you begin to see the threat that is posed to democracy itself.
If it were the military, and who knows, if Mattis or some 4-star general displeases el Commandante and the military becomes 'the threat', the 'well armed militia' may all that stands between you and the restoration of the monarchy. Only it will be the lad from Queens not our Queen who is in seated on the throne, demanding obedience, loyalty, reverence and love from all his subjects, with parades, pageants and public sculpture.
An afterthought: Can you imagine supporters of Malcolm X or the Black Panthers in 1968 creating a website 'Lyin J Edgar Hoover'? They would still be in prison, or these days, in Guantanamo Bay.