Couldn't help but quote this part.
You do know that MLP was a toys brand introduced by manufacturer Hasbro in the eighties, right?
That is was already declined in multiple media adaptations through the years, right?
Rainbows etc were part of it from the start, it has been mocked ever since.
It's very legitimate to associate a rainbow to that brand, it's been around for more than "two seasons".
To get back on topic:
Don't like the ideas behind those, I'll probably try to go for the warhorn or the sword.