I wouldn't say that is entirely true. I think that would have a certain effect on an individuals command of Lightning, but not a requirement. I say this because there are those who have used Force Lightning without having been on its receiving end. Certain beings have an innate ability to use Lightning.
Perhaps, but this is what Plageius said to Sidious in the Darth Plageius novel, and how the latter learned to use force lightening. Maybe its more to do with taking the rage and emotions etcetera inside yourself and channelling them i.e. Sith often use the dark side against Jedi/force sensitives in order to goad them into using the same power against them in angry retaliation - perhaps this is what is happening here.