Perhaps beware of people who give very good impression on making friends. Benefits of the doubt must be honored.
However, perhaps ask them, if there were anyone they knew that they tried to stay away from...and if yes, perhaps ask why? Then perhaps stay away from them. Don't waste time making friends with these lots. Perhaps make friends, but not really at the level of fellowship. Useful friends. Friends who only get to sit on the bench and watch you at work for the glory of God, but they do not participate, they do not share a fellowship with you, until they can learn to receive people they hate/despise. The more enthusiastic they are at first, the more cautious one must be against these. Because their chief goal is their own satisfaction, they're just trying to show that that is not the case, they may likely be very good at the practice, so beware.