One of the unique aspects of CRISPR is that it's easy (relatively easy) and cheap to do. It can be done in small labs without government grants or investors. It can be done in secret, and it can be done by people who don't care about the ramifications of the outcome.
When nuclear weapons were developed, we (humanity) were lucky that they required highly enriched, expensive, rare, difficult to handle, radioactive isotopes. This meant that even though he basic "formula" for a nuclear device could be understood by a high school kid, it was still very difficult and expensive to actually produce a working device.
The same inherent throttling mechanism does not exist with CRISPR, so this one is going to infect civilization very differently.
It goes without saying that if humanity exterminates itself then the issue will go away. But it's quickly going to be easier to manipulate genetic codes and therefor organisms, than it will be to change the environment or clean up toxins. The human organism is going to become extremely robust as this technology spreads through our gene pool because we're going to need to use it to defend ourselves against a more dangerous environment and more dangerous competition from within our own populations. The Red Queen principle will drive artificial selection just as effectively as it did natural selection.
The tall, beautiful, tough-skinned, strong-boned, super-intelligent, people with enhanced lung capacity, improved immune systems, no coronary disease and no genetic diseases, will quickly come to dominate the population simply by surviving better, not to mention being on top of the list for "best mates". Then there are going to be the new races, the green-skins, the purple-hairs, the ones with tails and the ones with claws.
Sounds like sci-fi doesn't it... People haven't recognized CRISPR for what it really is yet.