Satan separated himself from God's love. That was the beginning of evil. Hatred, judgment of other religions, name calling, disrespect, disfellowshipping, and shunning is not love.
Evil is the absense of love. However it masquerades as God's light. Servants of Satan attempt to take God's place. They try to represent God and command obedience.
The way to know who you're dealing with is to ask two simple questions. Do they teach love for all people like Jesus did? Or do they teach hatred of 'enemies', isolation, and separation?
(Note: JW's believe separation from the world and breaking up families is required by in order to follow Christ. This is one of 'Satan's lies'. It's a twisted and flawed interpretation of God's Word. As proof, read 'isolation from the world')