This is just a variation of the slippery slope argument except this slope doesn't seem very slippery to me. Gun rights have been getting stronger in the US not weaker, courts in recent years have decided that the 2nd amendment is an individual right and that it is incorporated against the states.

I don't see how a libertarian, as many gun advocates but certainly not all, can make a rational argument for preventing a private company from selling smart-guns to individuals.