How hard should it be to open a knife?

I was looking to buy a folding knife at Canadian tire so I asked to look at some of them. When I tried to open it though, I had to use one hand to hold the handle and the other to open it with the stud. When I asked the guy he said that was they way it should be. Is it? And if it is, what's the point of a thumb stud, couldn't you use a fingernail nick?