To all the questions, I would have to answer YES. The first one depends on whether or not their injury could have been avoided and became a last resort, but still, YES.
I think the tendency is to think we must be able to whip all the folks in all the other arts or it isn't effective.
Personally, I don't agree with that. I realize you don't either, and you're just pointing out that there are aikidoka that may have this tendency. People question the effectiveness I think because they don't understand the static, basic exercises or what they are for, especially in the beginning. Someone here said it best when they described Aikido as preparing to defend oneself from different "types" of attacks, and not limited to just shomenuchi, yokomenuchi, etc, etc, etc. You must learn to walk before running, and the average Joe that joins a class for a week and leaves is usually because of a lack of patience. They want to get right to the running and learn how to fight, and when they learn that aikido is not fighting and that it's a complicated MA to grasp, they leave. Aikido isn't for everyone, not everyone has the patience or mental attitude to continue.