fortunately there are 17m people who are not so childish
It's childish to choose where and when to spend one's own hard-earned money?
Would you say that it is childish for me to boycott products containing palm oil, or tax-evading companies like Starbucks, or companies which aggressively marketed baby milk in poor countries? After all, people might lose their jobs!
Or is it only with regard to Brexit-supporting companies that it is our (entirely mature and grown-up) patriotic duty to pour our money at them?
You could conversely reflect that, if people are choosing childishly to spend their money with (say) Remain-supporting companies, maybe those might have a chance to do better in these difficult times and thus secure more jobs? Whereas, as a Brexiter you presumably believe that golden times of unparalleled wealth have been bestowed upon us - so why would any company be doing badly??