Although not a common usage, in British English, "snapback" is a retort intended to be witty or derogatory, preferably both.

Absorbing words from other cultures is one of the ways in which all languages develop. So the use of a word from another culture is usually just that, using the word, generally because it expresses something that the language doesn't already have. Examples in English would include schadenfreude or zeitgeist from German, or hygge from Scandinavian languages.

The language and, to a large extent, accent of youths in London is mostly independent of their racial background, combining London English, Caribbean, and Asian words and grammatical constructs. Would you stop that as well? To this generation, they speak like that because the people they know speak like that.