A quick question about the changelings........

The changelings take the form of somepony you love then feed off your love for them.
The love has to be directed at the changeling. For instance, Shining Armor's love was directed at the False Cadence as he thought she was the real Cadence. The Changelings feed off of a sort of deceived love.
Since everyone knew the truth about the changelings and nopony was directing love towards them, they weren't able to feed off of it.

The way I explain it was that Cadance's love powered up Shining Armor, allowing him to create a spell powerful enough to defeat the Changelings. But you are right, if they used just the power of love, it would've helped the Changelings...

You have a point.

Well yeah that kinda makes it feel weird... Anyways I thought they used it for being able to change into non ugly ponies and the love candance gave was to help power shining armor which helped him able to cast that awesome bubble shield to rid of those... So really the whole point is she was and wasn't defeated by love... :/

Maybe. Maybe-a not.

I think that one burst of love between the two, plus a bit of magic, I think, was too powerful for the Changelings. Therefore they were blasted away from Canterlot.

I always assumed it's like with humans and iron. We need it in our daily diet, but it needs to be in the right form to be digested. Raw iron can be bad for our organism, and being whacked over the head with an iron pipe won't benefit us at all.

So I suppose the changelings can usually do something with the love they receive as a placeholder (which is a kind of passive, friendly, embracing love) that makes it easily digestable for them. But love that is thrown at them like a weapon, kind of an offensive, aggressive variant, is too raw and in the wrong form to be digested, so it can hurt them.

my thought is that the love gave shiningarmor his powers back to make the shield that blasted the changelings away ._.

it could all boil down to one simple thing, too much of it within too small of a time frame, creating an overload. See, no matter who or what you are and what you run off of, there is always three limits, one is how much you can take in, or capacity, two is how long you can hold it before it runs out, and three, how much can you take within a certain amount of time. The last limit could have came into play when they were defeated, it could have surpassed their limit in how much they could take in within a short amount of time. Think of it as charging your laptop or mobile, or as a fuse, you cant simply just run 100 volts into your device to charge it withing minutes, that would over load it and make it explode or have another dangerous result, same with a fuse it has a certain limit within a time frame, the changelings are the same, they run off of love, but they are governed by the same three limits that we all go by. It prevents them from going zero to god of the universe in a split second.