To me, "argument" means "A logical (or, at least, putatively logical) progression from premises to conclusion". "I have seen a blue Martian" is not an argument. If it is implied that you are wrong because of this, then "You are wrong because I have seen a blue Martian" would be the argument, while "I have seen a blue Martian" is a premise. So, in my nomenclature system, the issue is that many arguments/conclusions are left implicit. People often aren't even consciously aware that they are leaving the most important part of their argument unsaid. I find that often, much of responding to people consists of badgering them to make their arguments explicit, to little success.