The theory of relativity is quite real. If you are living on a ship at .99 C, time passes very slowly indeed. It doesn't take 5 years to you to travel 5 light-years. It would be a matter of months, IIRC. He's saying that technology like that in terms of the life-span of the entities in the ship is quite tolerable.
Now if you are at 0.2 C, it's a different ballgame. It's not linear. At 0.2C, you are going to need a "generational" ship, being born, living, and dying en-route.
All that is moot if there is some way around the speed of light.
Tankie, what I meant by "show us you are there" isn't a fuzzy blob of darting light over Washington or London, I'm thinking "District 9" ships hovering over cities.