Against my better judgement I will try to unpack this...
I think this is a case where writing and humour got in the way of conveying a deeper message. Not implying that women can't have misconceptions about feminism but there seems to be a genuine attempt here, hampered by the fact that it had to be written within the framework of Sonic Boom.
The first half of Knuckles' statement about the "undermining of the concept of gender equality" has some merit. Explicitly calling attention to breaking of gender roles in media is an acknowledgment of said (forced) gender roles and to a certain degree removes women's autonomy by implying that most simply adhere to them. Certainly, one can also make the argument that any pointing out of women "breaking the mold" is a celebration of women's autonomy within a patriarchal system and their ability to break free from it. I think both stances are valid.
The second part of his statement, however, goes too far in the sense that it tries to explain what I did above but has to do so in a succinct way. Dialogue in TV shows has to be snappy, otherwise you end up with stuff like True Detective Season 2. This goes especially for shows directed at kids. The way Knuckles' statement is phrased, it sounds as if he is denying the existence of gender inequality whereas it seems obvious that Knuckles is bemoaning the "status quo". In other words, Knuckles isn't talking about how things are but how they should be. He is
for gender equality.
The message is further muddied by what Amy says before:
As I explained earlier, Knuckles is advocating for the autonomy of women. However, Amy, in evoking the metaphor of the "glass ceiling", an image that was coined by and gained traction within feminist circles, is talking about external limiting factors. Essentially, Knuckles and Amy are talking about two very different things here, which is where the problematic nature of Knuckles' statement stems from.
On the matter of mansplaining: It is true that Sticks the Badger could have delivered this speech. She is visible here on the left and clearly part of the conversation:
And this is another instance where the framework of Sonic Boom got into the way of the message the writer tried to convey. In this scene, the humour arising from the fact that it is Knuckles delivering this little speech, is intended to be the vehicle for the writer's message. What the writer is trying to say is that even a self-professed "meathead" like Knuckles can be a feminist but by doing so she inevitably puts him into a non-feminist position i.e. making him "mansplain" gender equality to Amy. Through this constellation of characters and the choice of humour as vehicle, the writer has essentially written herself into a corner. It certainly does not help that his explanation is flawed but I am willing to give the writer the benefit of the doubt here.
One has to also consider the nature of the show here. Sonic Boom does frequently break the fourth wall and feature self-deprecating humour. I am an advocate of the death of the author but Knuckles' comment can be seen as a meta-commentary on the cliched
"You Go, Girl!" trope, essentially making him the writer's mouthpiece.
So to conclude, this was not a very effective way to introduce feminism and gender equality to children but I think the writer had the best intentions. I think it's important that TV shows for children try to tackle heavier subject matters like this but they also have to be very careful about it. The mere intention of conveying a positive message does not absolve one from potential missteps.
Now excuse me while I go to bed and think about why I am analyzing Sonic fucking Boom in the year of our lord 2017.