Sure, Virgin is building a "millionaire thrill ride". I don't dispute that. But more broadly useful technical knowledge and expertise will still be gained in the process. Furthermore, the test pilots know the risks, and accept them willingly; I'm sure if Virgin asked for volunteers, there would be a long line of people (both qualified and not) lining up to test these things.
If you're going to criticize it for not doing enough to help us get to Mars, you might as well criticize any and all non-essential spending of any kind that doesn't help us get there. Or if you really want to look at the cost/benefit angle, should we not be prioritizing fixing the problems on this planet first, before we embark on the exceedingly expensive and dangerous endeavor of putting humans on another one (which, lest we forget, is extremely hostile to Earth-based life)? If we are (as the author seems to be) worried about a "dinosaur killer" asteroid event, we should put the money into figuring out how to detect and deflect incoming asteroids. Seems to me that would be much more cost-effective, and have higher odds of success than evacuating humanity to Mars.