No, it doesn't. It's a spin-off and it does not bastering mlp in any way. By your logic, all the awful stuff (EqG is not awful stuff, though)
that, for example, Star Wars franchise has, somehow spoils original films, which is not true completelly. I've only seen 7 films, and all the bad things that were filmed in Star Wars universe, does not affect me in any way. Even if I watched them, it would not spoil original films. It might spoil flims in my head, but this is completelly subjective thing that would exist purely in head. Or, in your case with MLP, in your head.
I'm not lying, it is the same product. You said that it cannon't be under "my little pony" franchise because it got humans, but this is flawed logic. First in all 3 films we see ponies and Equestria (which is only logical, as EqG is a spin off from MLP). Second, even if there weren't ponies, it would not spot exist under "My Little Pony". Imagine MLP episode where we see no ponies (Instead, only Dragons, for example). There's no ponies, so by your logic this is not MLP?
In conclusion, it's only logical that Hasbro made it a spinoff. It happens in same universe (just in different dimension), it got characters, it got ponies and so on.
I don't see how this theory is related to the topic. Elaborate.