It depends on what one sees as reasonable (also see the difference between reasonable and rational). Take the gun control that you referenced as an example. It's likely that there is a vast difference in knowledge of the technical as well as legal aspects of firearms between gun owners and non-gun owners. So the law could be rational, but the two groups could differ on the reasonablenes. I see the slippery slope argument less today than I did in years past.

In my opinion, most proposals by either side on a variety of topics are not good options. They have become hard-line battle cries for their respective party in order to motivate hardcore supporters to come out to vote, particularly in the primaries in which the radicals comprise a larger share than in general elections.