You don't have to use Ruby/Python/PHP/Perl/node.js to have an open stack. What happens in 3 years when his bizpark runs out? What happens if he is successful before then and is running many servers and DB instances.... What if he need to re-arch to support HA?
Its almost like his argument is.. meh.. in the short term running a Microsoft stack wasn't overtly harmful, since its what I am used to I discarded other considerations...