I thought the arguments would be obvious to a programmer, but if you insist...
First off, everyone deserves basic respect and to be treated with dignity. Animals deserve respect and dignity as well (although we don't say "please" and "thank you" to them - I'll get to that in a moment). But you said "everything" deserves respect. That is not true.
You don't teach politeness, or manners, or anything else, as a series of actions to repeat unthinkingly. You teach by forcing them to consider the reasons for doing certain things. There are obvious reasons to be polite to other people. First of all, other people understand what "please" means. Animals don't, and computers aren't sentient. But over-archingly, the value behind treating others with respect and animals with dignity is that life has value. Degrading other living things is ultimately degrading ourselves. If we don't treat them with dignity, what can we expect in return?
Now, if you want to argue that Amazon Alexa is a sentient being worthy of polite respect, that would be a different question. But the argument against teaching a child to be respectful to a machine goes beyond just the obvious dystopian implications. The ultimate reason it's a bad idea is that like any form of obedience training that leads to irrational outcomes, it is ultimately rejected and ignored, because the logic and rules behind it were not inculcated, only the actions.
To sum up: You don't teach rules by teaching how to follow them. You teach rules by teaching why they exist, and when to apply them. A child who says "please" and "thank you" to a machine has not learned any values or learned the point of why we say those things to each other. In fact, it makes the words meaningless. If all you want is obedience and you think your kid isn't bright enough to learn when and when not to apply certain behaviors, then you can try a shotgun approach, but you won't end up with someone capable of thinking for themselves. To me, raising an autonomous person capable of making judgments about new situations is the goal of child-rearing, but then again, I'm not an authoritarian.
[edited for typos]