Whoever told you this is just concerned about you. Many people interpret 2 John 9-11 to mean they should not allow Jehovah’s Witnesses (or Mormons, etc.) into their homes.
2 John 9-11: Anyone who goes too far and does not abide in the teaching of Christ, does not have God; the one who abides in the teaching, he has both the Father and the Son. If anyone comes to you and does not bring this teaching, do not receive him into your house, and do not give him a greeting; for the one who gives him a greeting participates in his evil deeds. Jehovah’s Witnesses do preach “another gospel”—a “different Jesus.”
If you are not firmly, SOLIDLY grounded in your Christian faith and spirit-filled, then I agree with those who have warned you against allowing JW’s into your home. As Walter Martin once said, the average Jehovah’s Witness can make a doctrinal pretzel out of the average Christian in about 30 seconds. They are trained, week in and week out, to attack central doctrines of the Christian faith, and they are very good at what they do. If you are not firmly grounded, they will have you confused in minutes.
If you ARE firmly rooted in your faith, if you have a personal relationship with Jesus Christ and are spirit-filled, then I would say—by all means, invite them in and use the opportunity to witness to them about Jesus Christ. Give them your personal testimony, because it is one thing they can’t argue with—your own changed life as a direct result of your faith in Jesus.
Some background on the verses from 2 John is that in the early church, there were no church buildings. Christians met in their homes for worship and teaching. The verse refers to allowing false teachers a platform from which to teach their false doctrines (heresies). It really does not apply to allowing people from aberrant “Christian” sects to sit in your living room. If that were the case, you couldn’t allow any unsaved family members (or plumbers, electricians, etc.) into your home, either.
Before you open the door to them, however, I strongly suggest that you research their peculiar beliefs so you will be prepared.