Unlike the majority of commenters I have both worked in parts of the government where I perhaps had access to more information about this sort of thing than most do and also lived through a terrorist campaign that saw death and destruction on the streets of the country I was living in for decades.
That must have been very traumatic for you. It explains your ideas, but it doesn't make them right. If someone tries to smash me, I will do what I can to defend myself, but I will not, like that ignorant woman did, refuse to sit next to a Sikh on the plane just because he looks different. I will not judge people on the basis of their appearance and I will not refuse to give strangers the benefit of the doubt. Are you suggesting that if someone gets beheaded in the street, or a shopping plaza gets blown up, that we should all grab guns and rush out and start mowing down everyone that we think might look like a Muslim? What are you suggesting?
I'm sorry, but it's human nature to discriminate, especially based on fear. You can be aware of it, and manually override it, but if you didn't have the ability to discriminate you wouldn't be safe to be by yourself (Nor would you be able to tell one person from another).
Logic is the thing that helps people understand that their fear is irrational, but to suggest you never do it subconsciously, simply isn't correct.
I do not believe for a second that geektastic is suggesting that a beheading causes everyone to kill everyone else from the same race as the original offender, and I think you KNOW that.
I think he is saying that if someone identifies themselves as part of a terrorist group, they are to be treated in accordance with what the government or acting leadership of their community has decided is appropriate. In some countries that is death, others, it's prison, expulsion, or exclusion.