In general? There needs to be one person with the authority to make the final call on the question. That one person needs to hear the bikeshedder, not until they stop talking, but at least until they start repeating the points they previously made. Then they make the decision, and they don't revisit it without sufficient new information.
If the bikeshedder can't accept that, then you need to get rid of them.
Whats the point of saying this? Do you really want to take it offline or do you just want them to shut up?
If you absolutely have to ask a question, try:
“Why is this the most important thing for us to discuss right now?”
Or if you’re OK making a statement,
“I don’t think this is important enough to continue discussing. How do you want us to proceed?” And then if their idea isn’t insane just say, “OK, let’s do that and move on.”
The point of "taking it offline" is that they stop wasting everyone else's time with it - they only waste one other person's. Depending on how pathological they are, that may be enough to stop the bikeshedding, because 1) you've just told them they're going on more than the topic deserves, and 2) they can't hold everyone's attention, just yours.
It also effectively says "This isn't the most important thing for us to discuss right now".
But it's important that they have a chance to "be heard", both for their own psychology, and because even if they're a bikeshedder, they aren't always wrong. You just don't want to waste more of the group's time on giving them the chance to be heard.
> The point of "taking it offline" is that they stop wasting everyone else's time with it
So you’re deciding it’s a good idea to waste your time and their time? Isn’t there work to do?
> It also effectively says "This isn't the most important thing for us to discuss right now".
Don’t effectively say it. Just say it. They’re an adult and can understand when they don’t get their way.
> But it's important that they have a chance to "be heard"
They had their chance to be heard — in the meeting. And if you’re meeting them “offline” to stop wasting everyone else’s time, are you actually hearing them or are you trying to trick them into thinking they are being heard?
Feels like a horrendously frustrating way to work — holding little side meetings to pretend like you care what somebody has to say so you can avoid telling them they are wasting everyone’s time.
Work is work. Sometimes ideas are bad. It’s not Little League where everybody gets a chance to play in every game.
In general? There needs to be one person with the authority to make the final call on the question. That one person needs to hear the bikeshedder, not until they stop talking, but at least until they start repeating the points they previously made. Then they make the decision, and they don't revisit it without sufficient new information.
If the bikeshedder can't accept that, then you need to get rid of them.