Can there not be an assumption that we already do not approve of these actions?
I wish that were the case.
But given the image cultivated by and for Islam in recent times, it just isn't.
Blunt and somewhat unfair, I know, but it is the truth. You have a serious PR problem and it is naive and blind to not see that. Perhaps prior to 9/11 and the London subway bombings and all that came after you could have relied on the assumption you speak of, but not today. These events put the spotlight on Islam in a negative light (which prior to these events was hated by some but known to relatively few in the west, and to most of us was just a remote somewhat irrelevant religion like Sikhism or Hinduism. Mohammed Ali was muslim I believe? I don't think many cared).
Once Islam was in the spotlight, yes the western media did villify it and yes there are people out there who are blindly following that media and who hate Islam and muslims, never actually having interacted with them. These are mostly conservative Christians, the tea party type, those who went visceral at the "9/11 mosque", which was ridiculous. These people are your simple bigots.
Others in the west saw this and instincitvely defended Islam, simply becuase it looked like it was being blindly and unfairly attacked by these people. I am one. I met Skavau (also on this board) on Paltalk in the social issues section while I was doing that. I, and others like me, actually went to the effort of going to places like that, and here, and other places around the internet and in real life communities to discover what exactly Islam is and who muslims are and if we can co-exist and if we should defend them from these crazies (the crowd in the paragraph above).
In doing so, some of us actually became muslims. So there is a plus for you. Others of us however encountered more hateful muslims than expected, and discovered distasteful ideologies within Islam that even the friendlier muslims do not oppose, or at least not vocally. Things like homosexuals and apostates deserving death. It is hard to truly respect a religion that considers it just for you to suffer in hellfire for not adopting it (this applies to Christianity too).
We also encounter a culture within Islam that is just as tribal as the people we see attacking it. Muslims siding with muslims, just because they are muslims, even when they are wrong. "Brothers" and "sisters" vs "Kafirs". The us vs them mentality that we looked to defend muslims from turns out to be just as propped up by muslim communities themselves.
It is rare that I have seen people like the gentleman in this thread I responded to above with such a live and let live attitude, which is why I replied to him in an encouraging and friendly manner. I would LIKE the assumption you speak of to be one that we would have of people when we learn they call themselves muslims and follow Islam, but it will take some doing to get there. More people like this gentleman I was replying to is a good start.