I've downvoted this, since without any statistics to back it up, it's merely repetition of a common, unsubstantiated right-wing meme.
A search along the lines of "arrested assault robber" shows many cases reported in the Daily Mail, Sun, Mirror etc where the opposite happened, but only a single case where the bystander was arrested -- in that case, because the robber died [1].
Anti-social behaviour and minor criminality is the result of decades of underinvestement in education, regions outside London, austerity and an unbalanced economy [2].
[1] http://www.telegraph.co.uk/news/2017/07/16/have-a-go-hero-ar...