I see it as more of a reminder and to pay attention. We all have ranges/spectrums at which we operate. You can say, "shouldn't you just be kind to everyone", and the answer is, "yes, of course". But then, how that kindness is shaped and applied – for example, kindness can be offering help, or waiting to be asked for help (but being prepared to help). I think it's ultimately about awareness of how you can be kind in different ways.
For those that are deemed less intelligent, that kindness can take the shape of increased patience with things that seem obvious or easy to others, whereas for folks operating at a level more similar to you, you might behave differently justifiably. This is just one example that crossed my mind in this case.
We understand that dealing with children and dealing with adults is frequently different, and we wouldn't call that patronizing, we'd call it operating at the level appropriate for them. We might tolerate something from a children, and deem acceptable for their level, while tolerating the same thing for an adult in the same context would be considered unacceptable. There are all kinds of different ways to behave differently in different context.
So, yes, "choose kindness", but I took the statement beyond its face value to mean "exert yourself to be kind" and find out what that means in the most appropriate way based on the situation.