Just because something has been around for a while does not make it OK, its a weak excuse, either something is right or it is wrong, there is no middle ground in this case, either you have a secular system or you do not, and you have to be judged accordingly.
If something has been around for a while, but it is against the principles of secularism, then it should have been changed. The finances of religious organisations should not be under state control, it is totally wrong under a secular system. Cow protection laws should not exist, under a secular system. A law that classifies people or anything else according to religion should not exist under a secular system, I hope you understand the basic principle of what is wrong and what's right.
Everything has to stand the test of reasonableness, otherwise, it is open to direct criticism, so it remains wrong. Excuses can be made for anything. If your partner has an affair and you walk in at a wrong time,in a moment of emotional outburst, you kill them, it can be classified as a valid excuse, but, it is still wrong. So please, let's not use excuses to justify something that is clearly wrong.
Get rid of secularism, then do as you please, if you don't, then you are wrong.
This discussion is regarding secularism, so i will stick to that. Therefore, I will disregard the other points you have bought forward. It is a weak sign when a person has to deflect because they do not have strong answers for the core argument.