I think rephrasing the comment (as the post suggests) in terms of "that might work if we can [resolve fatal flaw]" is a good suggestion, in that case. It's a much less negative way to point out the flaw.
All you have to do is bring up the issue that you think kills the idea, you don’t have to issue a judgment.
If people can’t see that it kills the idea, then either you are wrong and it can be mitigated, or again you are wrong and it is not the issue you think it is, or you are right but you are dealing with a group of people that can’t see reason, which is something you would want to know anyway.
Instead of "what about <showstopper>?" you could say "I think that might be a reasonable solution. What impact will <showstopper> have on it?" and now you've validated the good and brought up the potential showstopper without shutting down the conversation about it.
It is asking asking a legitimate question in a neutral manner. It’s not supposed to be a microaggression. Asking a legitimate question should provoke discussion, unless discussion is fundamentally broken in your current environment, which again would be good to know.
In other words, don't ignore the atmosphere and end up killing it. Which is kind of the point of the article, I feel.
This is super condescending.
We very often have discussions around which solution we take. Often we take the one that we don’t like as much but we know how to make it work. The other solution designs are kept so we can revisit them sometime (or as reference for when somebody says “why don’t you…?”) with fresh minds and then see a new way around the problems we saw before.
In my experience the “<showstopper>“ is almost never a law of physics but a shortcoming of a dependency, either it’s implementation or architecture, or just some assumptions that are or have become invalid later on.
If the someone calling out the showstopper isn't the final approver or able to sway the group that it's a showstopper then suggesting a follow-up validation to demonstrate the showstopper can be a good strategy.
I think in general, not just in the workplace, people are very fine-tuned to noticing false compliments or underhanded criticism, and it's always worse than just playing it straight.
That's you. Plenty of other people will defend whatever they come up with regardless and need to protect their fragile egos.