The implication--and error--of this way of thinking is not only does it create a kind of "No True Scotsman" fallacy; but it paints a false portrait of being a Christian.
Christians are sinners, the same as anyone else. Christians fail, we sin. We sin a lot.
St. Paul speaks of the Christian paradox--that we are simul iustus et peccator, both saints and sinners--in Romans ch. 7. The role of the Law in exposing our sin means that the more we try to obey God the more sinful we actually discover ourselves to be. That it is as though sin were a wild beast, ready to strike, a force of nature within our own bodily members. So that what we know we shouldn't do, we do; even as we fail to do what we should do.
Toxicity in the Christian is sin. And the remedy, according to Scripture, is repentance. The Law must be preached that the old man be put to death, we are sinners, God have mercy on us and save us. The promise of God is that if we confess our sins, God is faithful to forgive us and cleanse us of our unrighteousness--and the Gospel is proclaimed by which we have that forgiveness, that mercy, that word of God which declares us forgiven for Christ's sake.
Sin, left to fester, erodes at us, gnaws at us, it sears the conscience so that it ceases to be reliable, because we quench the Spirit, we shut our ears to hear, we close our eyes so that we cannot see. And the cancer grows--and it very well may kill us, destroy us, unless it is nipped in the bud--that is why we must always mortify our flesh through the Law, and always cleave to Christ in faith through the Gospel, for by grace alone are we saved, we live alone by mercy. For all that we have comes from God, by His perfect love toward us; we must therefore always abide in Christ, abide at His cross, humble, grieving over our sin, rejoicing in God's forgiveness--that even as Christ lives so too do we live, and have life everlasting.
Any one of us who calls Christ Lord can spiral into the darkness--not because of God's unfaithfulness, but because we depart from God in Christ seeking our own "righteousness" apart from Christ, by choosing our own way rather than God's. And unless the Law hammers down, and the Gospel rescues and lifts us up; simultaneously killing the old man, the old Adam within us and giving life to the new man which is in Christ, then the warning stands, "there is sin that leads unto death" as St. John says in his epistle. Not all sin is deadly, but there is sin that is. The tongue is a tiny bodily member, but the tongue is an untamed beast says St. James, making hypocrites of us all, "With the tongue we bless our God and Father, and with our tongue we curse our fellow man created in His image. My brothers, this should not be so."
The danger in saying "there are no toxic Christians" or denying that such can exist within a Christian, is that it can lead us to a terrible place where we refuse to acknowledge it in ourselves, we stop recognizing that we are the problem, we are sinners, that our sin is a deep wrong which we need to rush and fall prostrate before God's throne of mercy and plead His grace, clinging to Christ and Christ's word and promise. We cease coming boldly before the Throne of Mercy and shut ourselves off from God--from the Holy Spirit who is always drawing us to Christ, cursing the inheritance we have received from the Father, trampling over the cross of Jesus Christ.
There are toxic Christians, and often it's us. Lord have mercy on us sinners. Jesus save us.
-CryptoLutheran
