It's as legitimate a tactic as any other. And I say that as the guy who usually has to take a 3rd headshot in the same place before I realise I need to change my route/strategy. Those bitching about it are either too lazy or stupid to change up their strategy, or even just their route, when dealing with campers. If folks think hard scoping is bad, try going against someone using 'no land beyond' and '1000 yard' at the same time, and is doing so while running you down.