There's some good advice from author/journalist Jonah Lehrer, in an article titled Groupthink dated Jan. 30 in the New Yorker.
Sometimes it seems like to criticize the views, ideas and actions of others is viewed as impolite - that no matter how constructively the criticism is intended, it'll be taken as hostile, as "enemy action". This mindset matches the mores of brainstorming - which, as recounted by Lehrer, "...[differs] from other types of group activity...[by] the absence of criticism and negative feedback." But Lehrer observes that this buys good feeling at a cost of less-good ideas -
"Brainstorming seems like an ideal technique, a feel-good way to boost productivity. ... [Yet] there is a problem with brainstorming. It doesn’t work."He goes on to recount the research behind this, and concludes,
"...[S]tudies suggest that the ineffectiveness of brainstorming stems from the very thing that [brainstorming's original proponent] thought was most important. As [UC Berkeley psychology professor Charlan] Nemeth puts it, “While the instruction ‘Do not criticize’ is often cited as the important instruction in brainstorming, this appears to be a counterproductive strategy. Our findings show that debate and criticism do not inhibit ideas but, rather, stimulate them relative to every other condition.”Please read the article and engage fully with it... then criticize in the comments.
[Brainstorming originator Alex] Osborn thought that imagination is inhibited by the merest hint of criticism, but Nemeth’s work and a number of other studies have demonstrated that it can thrive on conflict. According to Nemeth, dissent stimulates new ideas because it encourages us to engage more fully with the work of others and to reassess our viewpoints. “There’s this Pollyannaish notion that the most important thing to do when working together is stay positive and get along, to not hurt anyone’s feelings,” she says. “Well, that’s just wrong. Maybe debate is going to be less pleasant, but it will always be more productive. True creativity requires some trade-offs.”
And obviously, criticism can be delivered in a way that's unnecessarily hard on the recipient; the more we can make the criticism constructive & respectful, the better.
(& no, I'm not setting myself up as a paragon of virtue here, I'm presenting it as something worth practicing.)