You said I have a point and I laud you for listening to me without getting angry but you don't seem to have adjusted your view at all. Is a mugger a terrorist? Is a muslim who kills his neighbour in Turkey over a petty dispute also a terrorist? Is a drunk driver a terrorist? Is a person with mental issues who attacks people on the street also a terrorist? Would this German pilot BE a terrorist if he was a muslim but crashed the plane simply because he wanted to kill himself and take people with him? I mean your definition seems to be that if you inspire terror then you are a terrorist - so your answer to all my questions should be yes.
Doesn't this mean the word is essentially meaningless? Terrorist = criminal now? Don't you realise that if we make the word terrorist meaningless then we will simply need to create a new word for people who commit violence in the name of a cause? The reason we use the word terrorist is because the tactic was traditionally about carrying out some attacks on civilians in order to invoke terror among the general population and a fear that other attacks could get them in the future. This terror would give power to the group that carried it out and governments might have to deal with them and listen to their grievances - how is that in any way comparable to someone who kills just because they want to?
The point is that it is WRONG to say that a muslim who does the same thing as this german pilot is a terrorist. Anyone who says that is WRONG. Your solution to seeing someone being wrong is to be almost equally silly. They hypothetically mislabel this hypothetical muslim as a terrorist and your answer is to mislabel this german pilot as a terrorist.
Now you might have a point if you said that if the pilot was a muslim then peoples' first thought would be that this was probably a terrorist attack carried out in the name of a religious or political cause - but if the facts showed that to be wrong then anyone who continued to claim it was terrorism would be wrong. Why do you insist on being as wrong as these people you claim to be deriding?
Words have meanings...