Hi Sparkle: Because their communion is NOT a partaking of the body and blood, soul and divinity, of our Lord and Savior. Our Catholic communion IS.
To take Protestant communion would indicate that one views it as “equivalent to” Catholic communion. It is not.
To take Protestant communion would indicate that one accepted that as “equivalent to” or “acceptable” as Catholic communion. It is not.
A Protestant “communion” or “Lord’s supper” is symbolic (yes, I know that Lutherans and some “high” Episcopalians are CLOSE to Catholic view, but “close” is still not “exact”.)
I have deep love and respect for my Protestant sister, but I could not and would not take communion in her church. By doing so I am elevating THEIR communion to the level of Catholic communion. I am saying that their SYMBOL is the EQUAL of my REAL PRESENCE. It is not.
It is not “kindness” to make false statements just so that people are not “offended”. Sure, it seems “kind” to say that “communions, whether Catholic or Protestant, are all MEANT to be offerings to God, so I should take communion no matter where I am”. In the Protestant’s mind, what is being taken is at best something where the Lord is “under”, at worst just a “commemoration” of His death. But to a Catholic, communion is the body and blood, soul and divinity of Christ. And to receive communion which is NOT that is not just receiving NOTHING, it is blasphemous in its implied equivalency and certainly leads at best to moral “relativism” and at worst to moral INDIFFERENCE. . .
“Because you were neither hot nor cold, I spit you out of my mouth” said the Lord. Kind of makes you “rethink” the ideas of toleration/ acceptance/ “it’s all good”. . .