It's not disrespectful if you're invited to celebrate with them. But doing so without their permission is extremely invasive. An open festival is one thing. Lantern lightings, tulip festivals, Oktoberfest. But some holidays are deeply personal and it's simply more polite to be asked to participate. Especially when it's symbolic kinship, brought about by cultural exclusion and overcoming adversity with others of similar backgrounds.

Marketing promotion is where you sell a product under the guise of it being related to an event, place, object, or individual. Frequently rather than celebrating what it is intended to celebrate, the product makers only wish for financial gain.