The whole argument around stoning seems to go like this:
"Not all muslims stone people to death therefore islam is not responsible for any stonings and is peaceful".
That is about it. Hardly a convincing argument.
Sure, most muslims don't actually stone people to death themselves. But do they repeat and believe the verses in their quran talking about it? Do they voice support for certain groups 'to be killed' (regardless of who will actually do it and how).
Of course you pick one of the most barbaric acts and also one of the least practiced to give your argument the maximum weight but even then it's a pretty weak argument because islamic countries have a terrible record generally when it comes to things like this.
But still, having most muslims *not* stone people isn't evidence that islam does not contain commandments to do so or that it isn't condoned or supported in principal (i.e. death for those disobeying certain commandments).
Also, trying to apply things to a country level and then "counting the countries" is statistically dishonest.