Because the Human Shields(TM) are being quite stupidly used to protect infrastructure and army bases. The case could be made that they are in fact taking up arms against the US - an act that will justify the stripping of citizenship.
Your opinion is noted. I will continue to insist on the rule of law. If they are charged with a crime, they will be tried, and if found guilty, punished.
Please cite the source to back up your contention that citizenship can be stripped from them under the law.