When you sell the product you co-founded, you no longer get to have say. You can have opinions, but those opinions are no more important than those actually in charge. Those opinions might lean in the direciton of the general opinion or not, but it's just another tear drop in the rain.

If that opinion was so important that caused the co-founder to launch a campaign to wrestle control back, then let's get the popcorn. Now we have something interesting and that former co-founder's opinion suddenly has meaning. Otherwise, they really don't care and are just mouthing their opinons to see their like counts go up (but not their dislikes because, phew, those are hidden now)