Why are nonCatholics not allowed to take communion?

Several former Catholics were talking at work and one unreasonable aspect of the church they cited was that nonCatholics are denied communion. I wanted to say that by doing this the church helps them by preventing them from expressing a lie but really did not know how to say this gently. Why does the church deny nonCatholics communion.— can you help me say this better?

This link should be helpful for understanding why Catholics should not take communion in a non-Catholic church. If you have any further questions or concerns that are not answered by these links, please contact Catholic Answers directly.
Recommended Reading:

*]Ecclesia de Eucharistia (Note especially sections 43-46)
*]May I receive Communion with Lutherans?
*]Why can’t Catholics receive Protestant communion?

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