In my opinion, it's fine if a business doesn't want funds that come straight from an online casino for example, as long as they don't call a coin 'forever tainted' if it once came from such a casino.
If you withdraw to your personal wallet and then send the funds to cex.io, they should absolutely be accepted.
But then the casino could do the same and just transfer their funds to a new wallet and then use them again. Just trying to taint a coin for whatever reason creates a whole lot of unnecessary problems.
In the end its about protecting individuals fundamental right to transact. Blacklists are always subjective, not transparent and ultimately dont prevent crimes from happening. But they violate fundamental rights of individuals, and open the door to abuse and a dysfunctional economy. Money launderers and criminals will always find a way to evade them.
So we should try to reach more social consensus about that its absolutely essential for Bitcoins success to not accept any kind of taint being introduced by anyone. We gotta be completely stubborn here. Innocent until proven guilty, companies can still report criminals to law enforcement and it will be handled in court where it should be. Individuals fundamental rights are essential for a functional society and it starts with the freedom to transact. Even when not personally affected yet this is absolutely crucial for everyone. Privacy solutions can only help, but we also need awareness by many, to really push against it.