Another thing to consider is that one could use CRISPR to make lives worse.
What if someone gave Michelle Obama a very high chance of breast or ovarian cancer by giving her BRCA1 or BRCA2[0]? What if a dictator's competition got sickle-cell anemia all of a sudden, or lost their sickle-cell anemia before their trip to a malaria zone (which is also bad[1])?
If you could manage to give someone gene therapy, they're already screwed.
Consider that the only reasonable mechanisms for gene therapy on grown animals is to infect them with a virus (or something similar). If you can infect someone with a virus, they're already dead.
What if someone gave Michelle Obama a very high chance of breast or ovarian cancer by giving her BRCA1 or BRCA2[0]? What if a dictator's competition got sickle-cell anemia all of a sudden, or lost their sickle-cell anemia before their trip to a malaria zone (which is also bad[1])?
[0] http://www.ncbi.nlm.nih.gov/pubmed/12677558
[1] http://www.cdc.gov/malaria/about/biology/sickle_cell.html