In my opinion, the Sparrowhawk issue is much the same as the Magpie one. In the way that both have somehow become unliked by some people for doing a job nature intended them to do
Sparrowhawks have large territories and will be hunting in many gardens in the local area, the small birds are used to the threat and i don't personally feel it'll put them off feeding because of one or two visits a day
The best thing to do is plant something close to the feeders that the small birds can use as a shelter if attacked.Something thick and thorny