This was argued at SCOTUS 40 years ago in Sony Corp. of America v. Universal City Studios, Inc. The ruling was that VCRs do not constitute copyright infringement simply because someone could play infringing content on them.

Since the emulator allows you to play backup copies of games you legally purchased, the fact that it could also be used for illegally copied games is irrelevant.

There ought to be extremely heavy fines levied on the petitioner in cases of vexatious litigation like this.