Is it permissible for the owner of a laundry service to wash clothes the wearing of which is prohibited, taking into consideration that the customer may have an excuse (such as following another opinion, or wearing these specific clothes in front of their spouse, or placing something to cover the 'awrah), and that refusing to wash them may lead to the loss of customers?

If the prevalent use of the aforementioned garments by the people of the country is permissible, such as wearing them inside the house or under concealing clothes, then there is no harm in selling, sewing, washing, or ironing them. This is unless it is known that a specific person will use them for an unlawful purpose, in which case it is not permissible to assist him, due to Allah Almighty's saying: (And cooperate in righteousness and piety, but do not cooperate in sin and aggression).