I am not saying that I agree with this, but I would like to point something out.
Most kids who get made fun of with "anti-LGBT language" aren't actually gay kids. It might be a boy who for example appears to be more feminine than the other boys his age.
Not using any language to put anyone else down is a good thing in the long run cause it protects people regardless if they are gay or not.
But yes, a 5 year old doesn't need to be told about this stuff. And in fact if there ever is a "pledge" signed at school, it should be a pledge to not making fun or saying negative things about anyone not just one group.