If I don't do it somebody else will
"If we want to stop the defence industry in this country, we can do so. The result incidentally would be that someone else supplies the arms that we supply."Tony Blair
If you carry out the action then you are directly responsible. You cannot be held less responsible because it was inevitable. This confuses cause and responsibility
This is the confusion of can or ought with must. Just because someone carries out an action or expresses an opinion, this just means that it is a legitimate choice. It does not follow that everyone should make the same choice.