That is a absurd question. Would you feel joy at 6 million Muslims died through violence - or did you clap at the million dead Iraqis as a direct result of illegal invasion of that country by USA on false/fraudulent ground?
And to your question no I would not take joy. Indeed I am offended by your question which is loaded with false moral superiority. Neither would anybody in my social circle. There might be some twisted people who mught take joy out of that but then I am sure you have such people in America as well.
The point I made was when the writer says "sentimentally" is he referring to the mas murder of six million Jews his bastion of "modernity, science, rationalism, tolerance, equality under the law, freedom of expression and the dignity of the individual" carried out only 70 years ago?
No Islamist extremist will ever and I mean ever score that number of dead or drop to such industrial scale savagery. That is a record and will remain so. Therefore it comes across as bone shakingly annoying when those who turned murder into a industry now take the freakin pulpit and preach values.
To my mind these "lectures" are like the Yorkshire Ripper giving speaches on protecting fallen women. It sucks !!!