The real negative issue with Ethereum-based scams isn't that the scams themselves siphon up ether--that's effectively indistinguishable from any other market activity, legitimate or otherwise. The problem arises when people new to crypto lose money in a scam and are then forever turned off from the market, in the process telling anyone who will listen about how they got scammed out of ether.
The best thing we legitimate users of the Ethereum ecosystem can do is shine as much light as possible on scams so as to protect new/naive users from losing their hard-earned money.
Yes, these scams are very bad for the system. Ethereum was suppose to be a trustless system. Now we have all these tokens that are created and controlled by anyone who wants to make them. It is way to easy.... anyone can do it with a little ether. I think ethereum is a trust network. You need to trust the network and the code, but not the person, well sometimes you need to trust people or corps. You really need to be able to understand the token and the corp. or person behind it, because there is a corp. or person behind it. I guess in this beginning before the system is fully understood we will see this, but hopefully we will get the community educated(me) and maybe get a credit score going for these tokens.