So The Guardian et al are outraged because 40% of people tasered in London are black

[Burney]

Do cops have to actually shout “Taser” when doing the deed or is that merely a TV thing?

I think they do. They seem to shout it while it's being deployed - presumably so that their colleagues know the scrote on the ground has a fûckton of Voltage going through them and that it's probably best to steer clear until they stop twitching.