Earlier quoted context omitted.
Hmm... I don't see any conceptual reason why separating those things should require completely different languages, though.
Nobody bats an eye when you use Python for logic, sql for querying your database and regex for searching text. Unlike the front end, there are ample opportunities for "uniting" the backend in one language, yet nobody really seems to bother. I speculate that it's because these languages are better at certain things, just like having a non-executable language for data, helps keep the data, data only (cue angry lispers)…
I prefer writing queries using Django's ORM even though it is underpowered.