The current political climate and friction resulting from Canada's unwillingness to engage in fair trade with the U.S. has nothing to do with this. Canadian Customs has a long history of subjecting U.S. citizens to harassment, questioning, and secondary searches if they suspect you are a gun owner. Having an NRA hat, decal, or bumper sticker will often trigger intense scrutiny, as will the presence of hunting gear, camouflage hats, ammo boxes, or anything suggesting you are a gun owner.
It isn't at all surprising to hear the OP witnessed this behavior. It probably isn't universal among all Canadian Border Agents, but it's nothing new. Simply being uncooperative probably wouldn't make the situation any better. I guess you have to decide how important it is to visit Canada.
There shouldn't be any real problem if you fill out the Non-Resident Firearms Declaration Form, give it to the Officer immediately, and declare everything legally. But the TDS folks who wish to blame Trump for everything and anything will not hesitate to blame Trump for Canada's long anti-gun history... brought to Canadians and U.S. Citizens alike by the anti-gun Liberal Left. Sadly, we can't vote against anti-gun Canada politicians, but some of us use our brains and vote against them here... because we are able to connect the dots.
