The magic signature

Yesterday morning I was walking around when I was stopped by a guy who got close to me in a threatening way clasping a pen. He said to me : "A signature against drugs,please!"
Since I was a child sometime I meet cases like this repeating always the SAME sentence. STOP, please!!!
A signature against drugs? What the hell does it mean??? If I sign then problems related to drugs will magically disappear?? The actual fact is that who ask for a "signature against drugs" usually is collecting contributions in favour of communities that help drug-addicted people. I give with pleasure my contribution (I did it yesterday morning too) but pleeeeeaaaase ask me the the right question! I asked to the guy with the pen why he used the same old awful sentence instead of explaining the real reasons. He replied :"I use this sentence because it makes the people to come near!". Come near????? I saw with my own eyes elderly ladies discovering incredible speed skills as soon as they heard the terrible phrase.