Roisin - I've just double checked my post - and nowhere did I see the word 'stupid'.
I'm saying that your energies could be better off directed elsewhere.
You boycotting Israeli goods may well make you feel as though you are not contributing to their regime, but if you do not couple that with other actions, such as writing to your MP to urge the government to take action or campaigning to encourage the distributors to stop selling Israeli goods, then your gesture, I'm sorry to say IS meaningless. And I doubt that millions of people will join in the boycott, for the reasons stated by NeilOliversBurd.
It's not true you have no control there are lots of things you can do to make a difference. I just don't think this boycott is one of them.