I asked a question recently at my Facebook feed (in summary) if Christians should just let evil flourish. 
I am here with an answer. 

2 Thessalonians 2:5-8
1 John 3:8
Romans 8:9

There may be other passages but these helped me with the question. 

I heard a Minister of the Gospel say we are to stand against evil to prolong the time we can have to preach the Gospel of Salvation. Other than because GOD said so, that’s the best reason I’ve heard to date. 

We know from 2 Thessalonians 2:5-8 that HOLY SPIRIT restrains the Evil One from being fully revealed in this world and He restrains the rise of the Anti-Christ to power at this time. He will not always do that. 
From 1 John 3:8 I know that JESUS came to earth to destroy the works of the Devil, the Evil One. 
From Romans 8:9 I know that every SAVED person is indwelt by HOLY SPIRIT.

So, since HOLY SPIRIT is here to restrain the evil one; since JESUS came to destroy the works of the devil, and since all true Christians have HOLY SPIRIT living within us; it stands to reason that Christians must allow HOLY SPIRIT to resist and restrain evil in this world through us. 

So, what evil do we resist, restrain?
Every stinky form of it that is in this world.
How?
However, HOLY SPIRIT provides us individually and collectively with a way to stand.