Seagulls are more endangered than people think they are, though (red listed in the UK, population decline of over 50% in the last 40 years), in large part because humans took all their food. I think a fair trade might be that they won't steal our chips if we don't steal their fish? You know, rather than pointless animal cruelty. Fuck this dude.
We had an injured one outside my house last summer. Some local kids kicked it to death literally while I was on the phone to the RSPCA to find out if it could be helped. Kids suck.
Herring gulls are LC globally, but are now on the red list for the UK-specific bird conservation list (and amber for Ireland), due to the massive decline in population here. For black-backed gulls, it's amber and green respectively, so they're not as badly affected, but their UK population is still in decline. Whether a local population is worth protecting when a species is doing okay globally is a matter of some debate, of course, but I feel we would have lost something as a country if we didn't have seagulls anymore, regardless of whether the rest of the planet has them or not.