1. Each different organism has its own frequency signature, so unless two entities MOR (mortal oscillatory rate) is within the same tolerance range of a frequency, both won't be harmed by a single frequency.
The possibility of killing good and bad together arises when a program with many frequencies or a sweep program is used... In these cases, it is possible to kill both at once, so these are typically noted with cautions, or ways to benefit the good while killing the bad to shift the ratio back into balance.
2. This is a great blog article on this subject.
For more details, please check the link: