It is unlawful for any person knowingly or wilfully to resist, oppose, or obstruct the chief of police, any other police officer, the municipal judge, or other officer or employee of the city in the discharge of his official duties; or, by threats or otherwise, to intimidate or to attempt to intimidate any such officer or employee from the discharge of his official duties; or to assault or beat, or revile, abuse, be disrespectful to, use abusive or indecent language toward or about, any such officer or employee while such officer or employee is in the discharge of his official duties. (1986 Code § 14-45)