And if the shop owner is Jewish, it would be anti-semitism:

https://en.wikipedia.org/wiki/Anti-BDS_laws

I consider a boycott threat a non-violent threat; legal but an exercise of power that has moral dimensions.

Imagine if it said "post about it on Hacker News". That's not bullying

It's informing people that there is something a business is doing that they might not approve of and they might want to change their behaviour accordingly.