I overheard my neighbor say she had an awful day, so I anonymously sent her a meat lover’s pizza...

 I overheard my neighbor say she had an awful day, so I anonymously sent her a meat lover’s pizza.
She’s a vegan and I hate her guts.

This is an example of a joke with an unexpected ending. It makes you think that the jokester is doing something nice, when in fact the jokester is actually doing something mean. It plays on the false assumption that the reader has that the neighbor would like to receive an anonymous meat lover pizza (as most humans probably would).

The actions on the part of the jokester in the joke are rude because to send a vegan a meat-lovers anything would be rude as they don't eat meat.

This joke isn't very funny.