Both of these things won't destroy humans, if anything both of these will mean we push towards space exploration, terraforming and cybernetic augmentations even faster.
Maybe if think about a different way you may have a point. Namely if you'd argue that an cybernetic augmented human , (basically the only human life that could survive in 0g indefinitely) is a different species. So the more logical argument would be that no planet born species can achieve interstellar travel and colonization without giving up what it means to be said species. Simply because living on a planet makes it impossible to live in space. But living in space is required for a society to develop beyond the first development level, namely you need a large amount of beings living in space to build and maintain the truly awesome shit we could build. Like space elevators or a dyson sphere which would instantly solve the overpopulation and energy problem for the entire race (be it human or augmented human).
The more realistic answer is that a race sufficiently developed will have very little reason to fly about in space to meet races that are not on the same development level. Ask yourself, would you fly towards naked monkeys who barely can get to space if you had the technology to fly here? Why would you? What would this get you, apart from possible conflict?
A developed race would maybe have far-out stealth drones monitoring us but they would never fly here in person to do a Independence Day style invasion.
Or basically, the Fermi Paradox is speculative nonsense based on outdated thought models of the 1950ies. No sane species would even BUILD von Neumon Probes. Heck, we have enough sci-fi to make us vary of even developing real AGI's .. you think a race with FTL travel would build self replicating AGI drones? WHY?
(my 2cent) ;p
This comment was edited on Jun 12, 2013, 09:20.