For a perspective from the other side of the border (I'm from the US): I've been to Canada a few times as a tourist and on business over the past decade, never staying more than a few days. Every time, without exception, I've been on the receiving end of "aggressive", extended questioning, ranging from such oddities as "You're here for our free health care, aren't you? Admit it! Just tell us you don't have insurance!" to lines of questioning that suggest involvement with a drug cartel.
I've also been subjected to extensive physical searches of all my belongings. (And just to be clear, I'm a healthy, Caucasian, 20-something, US born-and-raised, male.)
I often think of most Canadians as being friendlier than a lot of people around the US, but immigration and border control aren't one of those areas.