I know you aren't, which is why I'm going 10 rounds with you. Yes the principle applies to everything, but you are talking about a wrong principle. The principle is that if you actively choose to engage in something, you have less rights to refuse the limitations that come with it. Here are some examples:
It is perfectly fine to hold a steak knife in your hand while in your kitchen. It is not fine to hold a steak knife in your hand when you want to get on an airplane.
It is perfectly fine to wear a Halloween mask while sitting on your front porch. It is not fine to wear a Halloween mask when you are getting your driver's license picture taken.
I would say to be honest that this is something where the choice just has to be made for us. We can't choose to live in a society without police, they're required and as such there are limitations that naturally come with it. To me, it's a simple case of the positives outweighing the negatives. I just can't get on board with an idea that officers should be barred from searching someone they believe to be dangerous so that person can go on to murder somebody. It seems like policy for policies sake. I understand you saying that people died for these rights, but I don't believe that certain rights are absolute, unwavering and the be all and end all. We use that argument regularly when discussing Religion for example in that things can and do change over time. Nothing should be exempt from being judged on its own merits as and when required. People did not die so that officers could not search people in the street for weapons and drugs. They died for a whole lot of things put together. Some of which absolutely remain to this day.
One thing I'd like to say, is that you pointed out to Raoul above how it's no consolation to the families of innocent deaths due to drones that they are the causality of war. I'd say the same for the families of those who may suffer at the hands of others be it violent crime with weapons, or heroin/crack cocaine sales when the police may have had a chance to act and couldn't because of this limitation.
I do completely agree with you and Silva when discussing how this is applied. But I see it as a separate issue from the idea itself. I am not for one moment proposing that a police officer should just stop and search somebody for shits and giggles, or target black people because they want to. Suspicious behaviour is often clear, and it's not always suspicious. Sometimes it's just not and a misunderstanding. In my opinion, that's no problem and life goes on. There is literally no harm caused. Where it goes wrong, is abuse of power and application which again, is a separate subject. If I for example was hanging about on a corner dressed in intimidating clothes and a police car went past and I started to act fidgety almost nervous and motioned as if to hide something then a police officer should be within their rights to search me should I be hiding drugs or a weapon. Yes, it may mean nothing at all and it may turn out I was just putting my phone away and just quite like dressing in all black and keeping my hood up at all times. I'd expect at the least an apology and no harm done. It's a million times better than me actually stashing a knife when I saw a police car and them doing nothing.
There obviously needs to be some kind of standard as to what constitutes suspicious behaviour, but it wouldn't be 'because I felt like it' or 'because he was black' and if it was, then again we have a problem of application and misuse of power.
One of the studies I posted in reply to Zarlak noted that most stop and searches were in relation to cannabis. And frankly, I would hope the police has better ways of finding the kind of violent criminals that would carry knifes and guns.
One of which, should be stop and searches IMO. Inconveniencing a few people on the street with nothing to hide before moving on is so so so so so much better than not being able to because of some ticker tape that means a violent criminal then shoots or stabs somebody. The positives far outweigh the negatives, in my opinion.
I completely understand your point about how the police target the people that they target, but that is a completely separate issue with regards to application, rather than the principle.