See Romans 14:5-12.
Note that this same argument could be applied to birthdays, anniversary celebrations, etc, etc. This would be an excellent way for the WT to get rid of some of their most ridiculous rules and regulations. Beards and pants are just the tip of the iceberg.
Reading the bible is ALWAYS the answer for dealing with fake Christianity that tries to enslave people like the Pharisees did.
"Who are you to judge the servant of another? To his own master he stands or falls; and he will stand, for the Lord is able to make him stand.
5One person regards one day above another, another regards every day alike. Each person must be fully convinced in his own mind. 6He who observes the day, observes it for the Lord, and he who eats, does so for the Lord, for he gives thanks to God; and he who eats not, for the Lord he does not eat, and gives thanks to God".