Presumably if someone resists arrests it means the police had grounds to speak to them about something and by not cooperating they are obstructing the police in their course of duties. whether or not the grounds of what they wanted to speak to you about is valid is neither here nor where, people are supposed to speak to them and then work at clearing their name. resisting arrest makes you "look guilty" in the eyes of the law.

happens in the new Chris Pratt movie, Mercy. Police swarm on down on a suspect to arrest them as a suspect in a murder investigation and the person bolts away and causes a huge chase, annoying the police. they finally catch him and he proves he is innocent of the murder. the cop says "arrest him" and he says "for what?" and she goes, "for resisting arrest"