What do you mean by "slightest doubt", no fly? There is an established procedure and police are empowered to test anyone performing an aviation related function (not just pilots) if they are suspected to be under the influence. This procedure is pretty robust but not quite the same as removal for "slightest doubt".
I can honestly say in 25 years plus of commercial flying I've never encountered an issue. I'm intrigued though, why degraded performance due to alcohol should be a cast iron front-page cause for tabloid hysteria while degraded performance due to fatigue is happily accepted by regulators and the travelling public.