You just need to know how to pick the right tool for the job, honestly. If you're comfortable with how the backend works works from a problem-solving perspective then you should be able to hop to different languages/frameworks without much trouble.
I wouldn't be quick to suggest just knowing one stack, as then you're kind of learning that particular group of technologies instead of the problems that they're solving and how to approach them. If the only tool you have is a hammer, then every problem will look like a nail.
For further actions, you may consider blocking this person and/or reporting abuse
We're a place where coders share, stay up-to-date and grow their careers.
You just need to know how to pick the right tool for the job, honestly. If you're comfortable with how the backend works works from a problem-solving perspective then you should be able to hop to different languages/frameworks without much trouble.
I wouldn't be quick to suggest just knowing one stack, as then you're kind of learning that particular group of technologies instead of the problems that they're solving and how to approach them. If the only tool you have is a hammer, then every problem will look like a nail.