Harassment

Can a city enforce its law on one person and refuse to enforce the same law on other people.

Within reason, yup. Police have discretionary powers. Just like two people with different histories can do the same crime and get different sentences. It may not always seem fair, but it happens.

Bias Harassment

We live in upstate New York and our next door neighbors harass us because our son is gay and have gone to extreams to pubically humiliate our son his friends and us.
A recent family gathering at our home was greeted with the neighbor's stereo speakers in the windows playing "who let the dogs out" while they screamed for 30 minutes "who let the fags out".
Our police department here told us that this is not a crime, it's
freedom of speech, however when another neighbor screamed
the N word at a black family that lives on our street, he was arrested..so this tells you the police can do whatever they want
to whoever they want.