Here's what I remember from my Ethics course at AUB (the same university from which the seven members graduated):
The Deontological current (championed by Kant): To do the right thing for the right reason. Meaning: Mashrou3 Leila decided not to open for the RHCP because they sympathize and believe in the BDS.
The Utilitarian current (see John Stewart Mill): Bringing the highest amount of happiness to the largest number of people. Mashrou3 Leila thought: Hey, it seems there's a great number of our fans who are being vocal about this boycott, let's please them and not do the opening act.
The Aristotelian current (Chiefly the Nicomachean ethics): Moderation in all things. Mashrou3 Leila finding themselves in a situation which was much more than a storm in a cup of tea eventually said, hey, let's focus on our upcoming Parisian concerts and get on with it.
But you see, the issue for me is this: If seven people (as they say in French "adultes et vaccinés") and who are graduates from a prestigious university no less, make a knowing, mature and responsible decision (regardless if we agree with it or not) and we do not respect it, then next time these seven people (who are more concerned about the future of their musical careers than we are, I am sure of that) vote in the upcoming elections, we shall not respect whatever their vote was. Multiply this by the number of people who are able to vote, and - bingo - let's not respect the outcome of the next electoral process.
My deductions do not make ethical sense according to all three major ethical currents, but, as long as we allow ourselves to make decisions on behalf of Mashrou3 Leila, we should be happy. Shouldn't we be?
To say this in Arabic about the band "chou bi fahhemon" (what the hell do they know?).
Quite a bit, I am afraid.