The premise is that homosexuals / lesbians quite rightly so, are often telling people that two things (persons) that are the same can be attracted to each other and making a good point in doing so.
Where as the magnet situation posits a paradoxical claim .. that being non-attractions of sames.
I suppose it’s a light hearted view of the old premise that insanity is the belief that two polarised opinions can both be believed in as truth at the same time.
Happy to help 😊
Peace.