I dont see anything wrong here, cryptocurrencies have become very popular, they know that they all, why don't the stars enter this wave and prove to their fans that they keep up with the times. There is mutual PR and it is normal, and even correct.
The problem that is see is that they are promoting icos as if they are a product that you can buy in any store but that is not the case, do you see any celebrity promoting Google or Facebook so people buy shares of that company? Because I do not.
An ico is a very risky investment that can make you lose all your money very fast and people do not really understand the risks they are taking when they invest, so while in a decentralized market is impossible to regulate what the celebrities do with their fame they are taking a huge risk too because if the ico scams its users then it is likely that will reflect in their image as well and that is something they do not want.