That's NOT going to end well. I think it's silly for devs and publishers to ask Steamspy to hide their data, but they're in their rights to do so.
A few people have made similar claims, so apologies for the fact that I'm gonna pick on you specifically here. In actuality, no, they are very much
not within their rights to do so (except inasmuch as you're allowed to ask people for pretty much anything whether or not they have any reason to give it to you.) They have no legal right to control of publicly available information about their own product, nor legal principle that would even remotely hint at providing such a right. (This is the same as people who want it to be illegal to have review sites like Yelp, basically -- understandable from a limited individual perspective, but obviously not happening on a systemic level.)
They also have no underlying
moral right to claim here -- creating a thing does not give you any innate ability to control how people talk about it, or prevent others from measuring it, or to avoid inconvenient truths that might somehow affect your business selling that thing. The abstract "harms" being described here are entirely premised on it
being virtuous to maintain a false sense of reality because people's reasonable reactions to true facts would be suboptimal for you, which one will have to work pretty hard to support under most systems of ethics.
In actuality, to feel like they have some innate
right to remove this data (as opposed to just asking for it and seeing if someone obliges) requires a level of petty entitlement or narcissism that far exceeds any reasonable, factual basis. It's the same instinct that drives companies to take down fanpages (even though they're forms of free advertising), or has the IOC sending DMCA notifications for ten second Olympic GIFs on Twitter, or leads to the kind of PR disasters and self-destructive lawsuits that companies only realize far too late have wrecked their customer base. It's certainly familiar, and something that will continue to happen until the end of time, but it's not something that should be respected and encouraged.
And of course, it's true the other way around: people don't have an innate moral
right to this information either. But Valve have chosen to provide an API that allows it to exist (and which publishers agree to allow when they sign up to publish) and someone's done the work to bring it together, and the result is a net positive for both consumers and devs/pubs, so.