I'm disturbed at how "citation needed" has become an argument. Since you are also making a claim (that it is not an improvement) don't you have an equal burden to provide citations? Are citations really what will make this argument?
It is also somewhat questionable to ask someone to prove a negative.
This isn't true at all. The negative is also often seen in the form of a null hypothesis. "There's someone in the fridge". "No, there isn't". Here is a case where we can prove a negative. Some negatives by their nature can't be proven, but as a blanket statement it's false.
You yourself mentioned that benchmarks were worse - this is proof of the negative, and you could have cited those benchmarks in your argument.
