That is an entirely separate matter. The fact that some Christians are hypocrites does not, in itself, make them non-Christians. Likewise, the fact that some materialists behave more kindly and compassionately than some Christians ( as explained above, what one means by kindness and compassion also matters a huge deal) doesn’t, in itself, make them Christians because, while Charity is essential to Christian life, moral conduct alone does not determine Christian identity.
Christianity involves faith in the transcendent God who has revealed Himself in Jesus Christ. It involves the worship of Christ. Philosophical materialism, understood as the view that reality is entirely physical, is incompatible with that faith, whether a particular person is culpable for holding that position is not for me to judge; only God can and will judge.
Within Christianity, Jesus Christ is confessed and worshipped as true God, not merely regarded as a great teacher, an enlightened bodhisattva, or an exalted angel, worship of Christ is integral to that faith.
Merely admiring Him doesn’t, by itself, amount to professing the Christian faith; nor is a purely intellectual acknowledgement of His divinity * the same as a life of faith, worship, and charity.
*Otherwise even demons would be Christians, for they definitely acknowledge Jesus as God, and they fear Him.
Let’s not muddle the waters, they are already muddled enough and will be immensely more muddled when the end times come, let’s not be complicit with that.
CCC 675
“Before Christ’s second coming the Church must pass through a final trial that will shake the faith of many believers. The persecution that accompanies her pilgrimage on earth will unveil the “mystery of iniquity” in the form of a religious deception offering men an apparent solution to their problems at the price of apostasy from the truth. The supreme religious deception is that of the Antichrist, a pseudo-messianism by which man glorifies himself in place of God and of his Messiah come in the flesh “
CCC 677
“The Church will enter the glory of the kingdom only through this final Passover, when she will follow her Lord in his death and Resurrection. The kingdom will be fulfilled, then, not by a historic triumph of the Church through a progressive ascendancy, but only by God’s victory over the final unleashing of evil, which will cause his Bride to come down from heaven. God’s triumph over the revolt of evil will take the form of the Last Judgement after the final cosmic upheaval of this passing world.”
I have also shown here Explaining one third of our sun going dark suddenly - #9 by 1Cor15.54 how the final deception will involve the destruction of the sacred, and thinking and saying that materialists can be “Christians” is a step in that direction.
I don’t want to make any step in that direction, if you want to do that be my guest.