Some people will hold it against him because some people are too stupid to see things in context. Rather than respecting him for taking a smart risk in pursuit of an important goal, they will just remember that he was once wrong about something and in a big way.

There are people who point at others' failures to bolster their own image by comparison. And there are people with fragile egos who are eager to see others in a negative way.

It shouldn't be that way, but it sometimes is, so I wouldn't say the career risk is zero. But I'm still glad he's doing it regardless of the outcome.

It's career "damaging" (I wouldn't say killing) because so many crackpots have attempted this problem that making a wrong attempt makes you look a bit like a crackpot.

I think he means if the stab is not serious but a troll. Of course, if it's a genuine and serious attempt, I don't think it should be frowned upon at all.

Seriously, best way to ensure people stop trying is to persecute attempts.