Yes, it is. And these people are celebrating and prepping for his appearance by following a lie over acknowledging the truth of God's Word.
Ephesians 5:5-12:
For this you know with certainty, that no immoral or impure person or covetous man, who is an idolater, has an inheritance in the kingdom of Christ and God. Let no one deceive you with empty words, for because of these things the wrath of God comes upon the sons of disobedience. Therefore do not be partakers with them; for you were formerly darkness, but now you are Light in the Lord; walk as children of Light (for the fruit of the Light consists in all goodness and righteousness and truth), trying to learn what is pleasing to the Lord. Do not participate in the unfruitful deeds of darkness, but instead even expose them; for it is disgraceful even to speak of the things which are done by them in secret.
... And Matthew 13:30 Let both grow together until the harvest and in the time of harvest I will say to the reapers, Gather ye together first the tares, and bind them in bundles to burn them: but gather the wheat into my barn.
I dislike being reminded of the tares or that they are permitted to grow with us, but ... remember ... there are tares.