> There seems to be a lot of potential for abuse in forcing everyone supporting any cause to publicly disclose their identity

That’s not what’s on the table—the issue in question is whether paying others to magnify your views with a direct aim at affecting policy is something one should be able to do anonymously. Especially if we restrict this to “paying enough money to buy a substantial amount of an entire person’s time dedicated to promoting your interests” then this very much does not mean forcing everyone who supports a cause to abandon anonymity, but even without that carve-out for small time donors, it still doesn’t.