Jisho

Well, I do not think the site would promote hate speech.
However, this is a dictionary/Jap-Eng translator. And when communicating in Japanese it’s important to know what is being said to you, and what you are saying. So while the definition is not offensive, it’s the slang term that is. The site can’t control who uses what as hate speech, although it’s unfortunate.

a dictionary wouldn't be complete if it excluded some definitions just because they can be of an offensive nature

casually addressing people as "fag" or "faggot" is standard on most Western chanboards regardless of how people who don't frequent those boards may feel about it

and the Japanese term has it's roots in the Japanese equivalent of those boards
so yes, "fag" is one of a handful of appropriate translations in this context

also if you take a closer look at the entry you will notice how this entry is labeled as "slang" and "derogatory"
as a new learner you will probably want to avoid trying to use words labeled that way in your own speech

There is a world of difference between using a word and defining a word.

If "offensive" words were not defined and explained then how would you know if it was offensive or not?

I would imagine the majority of Japanese language speakers would like to know if someone was using a derogatory slur towards them, especially if it is not their native tongue.