They don't need to boycott it - financial regulators can and have come down on banks and payment processors for allowing 'morally dubious businesses' [https://en.wikipedia.org/wiki/Operation_Choke_Point] such as payday lenders, firearms related companies, porn producers, and many more. There is a long history of this type of thing happening, and no one wants to get near an industry where their underlying ability to bank (and therefore interact with the financial system at all) can be yanked with a phone call.

Payment processor scenario: you need to select one, for example for the POS in your new grocery store. Your fanatical friend says that the evil heathens at provider X support porn and you should avoid payments from X. You want to appease your friend, even if you don't want to boycott porn; on the other side of the balance, in favor of using provider X anyway, no compelling business or moral reason.

It doesn't take many people to agitate, if they are sufficiently unpleasant and noisy and can't be easily written off as cranks.

This has nothing to do with boycotts or consumer choice. It's about regulation. If payment processors don't crack down the government will. No one votes for pedos.

Not many, but it just takes a few of the "right" people who know how to pull the strings: https://www.institutionalinvestor.com/article/b1s9f698vwhczr...