Do you suppose one of the reasons God tells His people to "come out from among them and be separate" is because He knew the power of influence someone who is not walking in His ways, can have on another who has claimed Jesus Christ, as in "what does righteousness have with unrighteousness, or what does Christ have with Belial"? I have observed this "power" (which of course, ultimately, is the power of the enemy to devour God's people) in the past 8-10 years, between dominate or people of "authority" over people who are weak-willed and followers, and it has been personally painful to watch. I have seen people compromise their former standards in the Lord, which they once were strong in, and lower them, because others around them, influenced them by demonstrating their carnality, knowingly or unknowingly. This had manifested in loose language, dress, materialism, the pleasures of this world, emphasis on physical vanity instead of on His internal values of character, and justifying evil in movies, books, etc, and calling it "good," because there was a little bit of redemption in them. Again, it's the enemy stealing the purity of God's people, and their saltiness in this world, by tainting their lives and witness to God's holiness and true ways. God's Spirit within me is grieved!!! Is yours?
Each gathering with people in our lives, must be put before the Lord as to whether it is His will for us to attend or not. Sometimes He has us go to be a witness of His light and love, and sometimes He has us stay. Again, it's the case of "the cloud by day" and "the fire by night"; the signs He used for the Israelites as they traveled through the wilderness. (Ex. 40:36-38) Sometimes the power of evil or unrighteousness, would be too strong for even us to resist, that He tells us to stay. Other times, even though that power of influence will be present in a gathering of people, He has us go anyway, to be the influence over that unrighteousness, and "greater is He that is in me, than He that is in the world" empowers the situation.
So, it's imperative that we, as God's people, SEEK HIM in every situation, especially since the times are becoming so evil in and through others, and licentiousness (doing whatever the "flesh" wants without regard to what God wants) is rampant, even in those who formerly called themselves His, and who still are deceived into thinking they still are. ("If you love me, you'll do what I command."-John 14:15) Many who call themselves His, think they can do whatever they want to do, and say they still love Him. He says that we cannot. These can have great influence on those who either don't know the truth, or because they are weak and give into the passions of the flesh, or because they don't seek Him and His will in any and all things in their lives. All these things, can subject anyone to be dragged into this influencing power of satan, and can cause people to forsake their relationship to Christ, or at the minimum their effectiveness.
Oh, how dark is that darkness that tells us we are in the truth, but really are getting further into the darkness, and don't even know it. Watch who you hang out with, for it was true in the past when it was written, and is becoming more apparent today that "a little yeast spoils the whole batch." "Coming out from among them," can be life saving, in the physical, but also in your relationship with God through Jesus Christ. Sometimes it's just a matter of what is most important to you: your own will, or being accepted by other people by compromising God's holy standards, or what He wants and desires for you, His child. Choose today who you will serve, for today is the day of salvation! We may not have tomorrow.