Lol. It's a global American brand that all their franchises earn hundreds of millions for. As well as giving free meals to soldiers involved in genocide it is one of a few globalized brands that truely represents corporate America and it is a way for people to peacefully protest against Americas total support of Israeli genocide and it's disregard for international law, specifically collective punishment of a population for the crimes of Hamas. The deliberate starving of Palestinian kids while IDF soldiers get free McDonalds meals a few kms up the road is abhorrent.
The Cork protestors aren't physically preventing anyone from going into McDonalds. They are entitled to encourage people to consider boycotting them as long as they do it peacefully which they are.
McDonalds and Starbucks have admitted the boycott movement has effected sales growth. That shows America that there are some consequences, however small for it's full support of Israel's almost total destruction of Gaza and the murder of tens of thousands of Palestinians. American politics is enormously influenced by big businesses like these, Trump goes out of his way to show how much McDonalds he eats so it's people's only way of pushing back and telling America it's out of order.
It also shows, like the fuel protests and others, that it is possible to achieve things through peaceful protesting if enough people buy into it.
