Honestly this was like the normal lesson of not judging a book by its cover. It shows that you cannot judge all Changelings the same, that they are all different. I loved how even Twilight got a friendship lesson of her own. It brings back memories of Season 1.
Really I feel as if this episode portrayed more of ponies being in the very wrong. Their racism against Changelings was shown. I doubt even with Thorax, that ponies will be okay with ALL Changelings after. I also believe that Equestria and the Changeling Empire (Or whatever it is called), will still be in a war type relationship.
I am a bit disappointed in Twilight Sparkle for not acting properly as the Princess of Friendship. If she is to befriend Discord, who actually did more damage to a city than the Changeling attack, then why would she not forgive just one Changeling? It is clear there is some form of racism or whatnot in here. But I rather not delve deep into it.
I do hope Thorax appears again later in the show. And I also wonder if he was the one in Ponyville during that one scene. I didn't like how he was portrayed, I just found the voice a tiny bit weird but that is something I can get over.
Not really much else to say except that this episode indeed made my melt heart. Guess it also did for Thorax.