The VMs aren't even close to "high performance" (although they are very wonderfully compatible), and the UI toolkit is not one (it's a document markup toolkit with buttons and such glued on, it's pretty awful compared to Mac OS's Interface Builder).
And any computer can run just about any kind of code now. Ask someone to download Python or LuaJIT and they can run your code.
Security models? In Lua, you can empty the environment and start fresh. You have a perfect sandbox with the flip of a switch.
I don't think the grandparent comment is sneering. I think he has an opinion that disagrees with yours.