Many, many Muslims are not part of this issue and would be disappointed at the actions of those protesting.
We are all the things you say but, in my opinion, we should be sensitive. That is not un-British. I have taught Islam many times and I have always avoided showing sensitive images but I have discussed the issue, of course, because children are inquisitive and will ask, "What does he look like?" Or, "Are there any pictures?". I have always said that within Islam, that person is considered so powerful and so important that pictures showing images are considered offensive. We have then moved on to other features of the religion or aspects of the mosque. Granted, I teach primary age children.
I deplore any kind of retribution or threat but I cannot condone what the teacher did as I feel it was insensitive.