State very clearly that your child "is being bullied".
Don't say "minor bullying". Don't say "low-level, niggly behaviour". Call it what it clearly is: bullying.
Then state very clearly that the bullying is making your child is miserable.
Next put the spotlight on them: ask what the school's anti bullying policy is, ask what the school intends to do about the bullying.
They may not even ask you for the specifics, as they probably know exactly what's going on. If they do ask, state clearly that your boy is being "verbally abused every day". If they ask for more specifics say that you know the abuse includes being called "gay". That should be enough for them to act.
Don't make them meeting about you proving that he is being bullied. Don't feel compelled to list a long "laundry list" of incidents. Stick to "I know my son is being bullied, what are you doing about it".
Be prepared, if the school (or the other parents) are sneaky, they might try and turn things around by saying something like "oh, it's funny you say that. We can see that the two boys play together and are actually good friends. Sometimes they fall out, like all friends do, and maybe your boy is too sensetive to that?"
If that happens, shut it down straight away. Stick to: "No, my son is clearly being bullied. What is the school doing about it?"