The standard for detaining someone is, and always has been, "probable cause."
Probable cause entails some element of proof. The crack rocks in someone’s pocket. The telltail sign of alcohol on one’s breathe while driving. The stack of illegal cigarettes sitting next to this guy on the sidewalk. Did the cops have anything for, ‘probable cause’, besides a hunch?
If the cops went to handcuff the fellow because he became argumentative, then that is wrong...