And that's why they ask "what you do plan to shoot?" "Whatever strikes my fancy and I don't want to carry around a big pack" is a valid answer, so of course they'll recommend a telescopic zoom, the artifacts are a trade off. But if someone is only doing portraits, macro, or whatever, obviously a very different lens will be recommended. Now people like you and me probably do all our research ahead of time and know exactly what you want, but sometimes it's nice to talk to someone with experience that knows what they're doing. Maybe the softness around the corners on the sigma lens really aren't as bad as they make it out to be so you can get that and save yourself $300 or whatever. This is something you'd probably never get at BB.
I'm still very much an amateur, but uv filters are basically worthless. If you're worried about protecting the lens, a hood helps keep things away from the lens, and if you drop your camera, you might get lucky like plenty others out there and only walk away with a broken hood.