The intention behind not letting it work for their competitors is immoral and potentially illegal. They want to do it to prevent their consumers to buy their competitors products for their family, even if their competitors product are better; just because they already have a device in the Apple ecosystem.

They are not "preventing" anyone from doing anything, they are simply, until now, refraining from improving their competitors devices by releasing their software for it.

Of course they prefer people to buy iPhones for their kids, there is nothing wrong with that, and there is absolutely nothing wrong with not actively working to make the experience of mixed Android-iPhone families slightly better.

There are literally dozens of cross platform messaging and video calling apps. Banning these would have been wrong, and possibly illegal, but they are not doing that.

It is immoral and illegal that McDonalds won't serve me a Chik-Fil-A sandwich.

This is such a great rubric!

The email we are discussing specifically says they want to prevent customers from buying their competitors products for their friends and family.

I don't know if they use the word "prevent" or not, but we both know that they are not in fact trying to literally "prevent" anyone from buying an Android phone. They just don't want to give them some of the benefits of iOS if they do so. No reasonable person would call that "prevent".

They are specifically and intentionally limiting the ways in which their customer can use their devices unless they buy more. Is that simple enough to understand?

No they don’t, they “limit” the way people can use Android devices.

Their customers cannot use their devices to iMessage their friends or family on Android.

A small software company is treated differently than one of the largest companies on earth, both from a moral perspective and a legal perspective.

Anticompetitive behavior is illegal for companies with a monopoly, and based on the leaked emails, it seems Apple's intentions were clear. The "monopoly" bit is still up in the air, but it's becoming increasingly clear the "anticompetitive behavior" bit is not.

This FaceTime news shows that Apple's lawyers are probably worried.

Reasonable people may argue that they have a monopoly on iOS apps, which could be problematic, but they don't have anything even remotely approximating a monopoly on video calling or messaging apps, which is what we are talking about here.

They also don't have any kind of monopoly on TV or music streaming, so there would be nothing wrong (and certainly nothing illegal) with keeping Apple Music and Apple TV exclusive to their platforms, so clearly they believe they will make more money by making them cross platform. Presumably it's the same with Facetime.