Saying "are you fucking insane? Only an idiot would come up with this", like Linus would, is also direct.. but, not particularly necessary in my opinion.
Something like "is there a reason you chose to do it that way instead of this other way that we have done things in the past?" might be interpreted as "This is wrong. Why didn't you do it the way I did it the last time I did something similar to this!? Please throw out what you've done and re-implement it my way."
This might have something to do with the assumption that the OP mentions: that everyone is aggressive and blunt by default, and this is just a passive aggressive form of the same. If this wasn't the norm, perhaps this subtlety wouldn't go unnoticed.
This leads to a situation where the sociopaths thrive by convincing the clueless that "we all must be kind" while, themselves, adopting Machiavellian ruthlessness, including publicly shaming the people who point out their hypocrisy: "How can you be against kindness! Shun the outsider!"
My working theory is that in small enough groups where, and this is key, the groups are largely self-autonomous/autarchic, the game can remain stable in the "all kind" state. From personal experience, I have seen that simply having small groups, but arranged in a power hierarchy, allows the sociopathic element to win the game by appeals to the remote, functionally indifferent master.
Can a company (or, indeed, a country) be organized this way? Can it prevent the Gervais Principle (http://www.ribbonfarm.com/2009/10/07/the-gervais-principle-o...) from winning out?
Dunno. Gonna try to find out.
I had a recent situation in which we were in a focus group and I followed the CEOs explanation of our plans for a particular feature with, "To clarify, we are going to be..." Little did I know the words "to clarify" irked and upset him as he felt undermined. I should have used the words, "To build on Jerry's point..." Needless to say, in several meetings after that he displayed aggression toward me, which then upset me and it was weeks before we sat down and cleared the air.
There is much subtlety in communication and interpretation that it can be maddening. One simple word or phrase can trigger extended bouts of unpleasantness and inefficiency. I do believe there is responsibility on both sides: In this world of ever quickening communication, one should choose their words carefully and one should not be so sensitive and take things too personally. It's my personal opinion that we have too much of a problem with the latter than the former, but then again, I'm usually the one on the other side of that situation.
 About working in warehouses. Stories persist from 2012 to just last year and Bezos was always around. Paints a picture of draconian working environments meant to save every last penny for the end customer.
 Can't find link, but just last week on HN there was something about working at Amazon corporate. Here is another link. Same sense of austereness and frugality (albeit of course perks shouldn't be expected), but there are also fundamental aspects of employees just not having a voice that really goes against choosing kindness in my mind.
The first author makes a stink of the fact (and mentions no less than three times) that one is fired if they are late the first week no matter the circumstance. Oh, the travesty. But then she even details the performance point system they use in which one is marked down 1.5 points for not SHOWING UP to work. And it requires 6 to fire you. You can actually just not show up 3 days to work and not get fired. Incredible. I mean really, she paraphrases a conversation she just happen to have with a woman in her late 50s about the tragedy of having to be at work at 5am the first day.
The second author's statements are full of innuendos such as "if someone talks during work hours, the rest are expected to shun them." No claim that this is written policy of course of which he could not back up. No, the only explanation being, "it's a subtle thing because they ask you to "report possible anomalies to your superiors."
The horrors of capitalism. Guess what? Working at a warehouse sucks, but after fully reading both the above articles it actually doesn't seem as bad as I thought.
And let's face it, we all like to get together and laugh heartily at bad code. It can be pretty fun.
That's why I'm consistently impressed by engineers who provide feedback free of pride. I've been lucky enough to learn from people like this and even luckier to work for them.
OK. To each his own. Use the style of the community you're in. The fact is that I don't take technical criticism as personal, so I really don't mind getting called out on my faults directly. It's like peeling off a band aid. Better do it fast and painfully than slow and painfully.