Cant is a term of disparagement. It suggests that the person using it is engaged in a criminal activity, which they are trying to disguise.
A cant is a system of speech created deliberately to foil understanding by outsiders. Shelta, which is used by the Irish Travelers, is the most elaborate cant. It has a complete vocabulary built from English, Irish Gaelic, and a few Romany words, with a system of phonetic alterations that makes even familiar words difficult to identify. It was indeed created so that neither the English nor the Irish people among whom they lived would be privy to their conversations. "Bloke" and "moniker" are Shelta words.
But the most well-known cant is Pig Latin, or "Ig-pay Atin-lay." It was created as a childhood game to divide the in-group (those who understand it) from the out-group. It is so successful that it long ago lost its ability to serve its intended purpose. I doubt that there's an American older than six who cannot understand it. (Do children speak Pig Latin in other anglophone countries?)
Surely there are many cants created and used by criminal networks. But that does not mean that every cant serves a criminal purpose. There are many other reasons for not wanting to be overheard. I suggested that AAVE is "like a cant" because sometimes people seem to use it for the primary purpose of excluding the rest of us from their conversation.
In any case, "cant" is not a word in most people's vocabulary, unless they're linguists, sociologists, police, etc. I wouldn't worry about it being misinterpreted, although I'll take your advice to heart just in case.
Argot is better, as it can also be used for people who have mutual interests, and who use specialised words. Train enthusiasts, and gardeners, for example.
These words have specific meanings and you can't interchange them on a whim. A cant is a particular kind of argot, but as you note, argots also include the arcane vocabularies of jewelers, psychologists, computer programmers, brewers and model railroad builders. They have no intention of leaving us in ignorance and if you're not careful they'll spend hours
teaching you their argot.
"Jargon" is another type of speech using specialized vocabulary, but jargon typically spreads out into the host language whereas argot does not.
The safest word is dialect.
Absolutely not. A dialect is a variant of a language that differs from other dialects in vocabulary, and usually also in phonetics and grammar. Standard American and Standard British ("BBC English" or "Oxford English" as we call it over here) are the two most widely used dialects of English, with Indian English a close third. Dialects invariably arise naturally, usually through geographic separation but also class separation. The key attribute that distinguishes a pair of dialects from a pair of languages is
mutual comprehensibility. It may take a person from Beijing and one from Chengdu a little time to get used to each other's dialect of Mandarin, but within a couple of days they'll get the hang of it. But a person from Beijing speaking Mandarin and one from Hong Kong speaking Cantonese (two distinct languages despite Americans calling them both "Chinese") will take years to achieve this, if at all.
The purpose of a cant is to foil understanding, whereas a dialect by definition is understandable. The two terms cannot be used interchangeably.
I can see calling AAVE an argot rather than a cant, since no one is going to admit that they use it to prevent us from understanding them.
Still, I'm not quite comfortable with that because argots and cants differ from the host population's speech
only in vocabulary. (Even Shelta arranges its fanciful words with both the sequence and inflections of textbook-perfect English grammar.) AAVE has considerable grammatical variation from Standard American--IMHO, its grammar is considerably different from all the standard dialects.
This is why most linguists call AAVE a dialect.
