Is celebrating Mother's Day considered an imitation of the disbelievers, and am I sinful if I do not inform others of its prohibition?

"Designating a specific day to celebrate the mother is a forbidden innovation (bid'ah muharramah). A Muslim must denounce it to the best of his ability, acting upon the hadith: 'Whoever among you sees an evil, let him change it with his hand; if he cannot, then with his tongue; if he cannot, then with his heart—and that is the weakest of faith,' and Allah Almighty's saying: 'And enjoin what is right and forbid what is wrong and be patient over what befalls you. Indeed, that is [from] the matters [requiring] determination.' Therefore, not denouncing it while being able to do so incurs a sin, unless a greater evil would result from the denouncement; in that case, denouncing it with the heart is sufficient."