Downvoting doesn't solve much in cases like this—all the top-level comments are political to one degree or another (mostly very political), and they're pinned to the top at this point by upvotes from politically like-minded people.
There are a bunch of downvoted comments from the less-popular political perspectives in the threads, but them being downvoted only decreases the quality of the conversation, because the greyed-out comments warn curious people off of participating in an increasingly hostile discussion.
The article itself is political, so why wouldn't the discussion be? The real question is whether HN wants political discussion, which at least in the past has been "no".
I guess the distinction I'm drawing is that the comments aren't interestingly political. The political topics that are left on the HN front page are usually there because the discussion is heavily moderated to keep things civil and interesting, and that doesn't seem to be happening here.
The top comment by tsimionescu is fine. Not great, but par for the course. The replies are at least mostly civil, but they're also mostly drive-bys.
The other top-ranked top-level comments range from uninspired to terrible. There's this one (which suggests that OP and I aren't the only ones feeling this way), then the usual "the right is ascendant" comment, then an insanely flamebaity comment (235 replies and counting) that begins with "clearly the author is ignorant" and somehow manages to go downhill from there.
Then there's a tired/wired meme and two single-sentence calls pointing to alternative alliance/free-trade arrangements with no further explanation.
The “clearly the author is ignorant” comment is only flame bait to people who aren’t up to date with how immigration has destroyed Canada. Actual Canadians are being displaced by people who don’t care about any kind of Canadian values. There’s people who hold the permanent opinion that immigration can do no wrong.
