Turning the tables on critical trolls

How to deal with the colleague/board member/voter who is quick to criticize whatever you're proposing?

It can't work/it's been done before/it's never been done before/you can't do it/we don't have the time/money/skills…

So easy to be right when everyone else is wrong, so easy to be confident when someone else is putting themselves on the line.

I start with this: do we agree that there's a problem? An opportunity?

Do we agree that we need to take action, that something needs to be done, that there's an opportunity here?

If we don't agree on that, then don't waste time listening to my solution. Before we do that, let's spend more time deciding if there's a problem or opportunity here.

Once we agree on that, then the response seems simple: "What do you think we should do?"

"Be specific."