Does Lemmy have any moderation tools for dealing with users that always vote down posts because they disagree with a community?
For want of a hypothetical example, say someone created a community dedicated to pineapple on pizza. What’s to stop people who strongly disagree with pineapple on pizza to subscribing, and voting down every post?

No they can’t, only admins or mods.
Lemvotes.com
We block that spying tool, so it doesn’t work on lemmy.ml . See here.
Security via obscurity🙄
See the linked thread.
I did! Most of the arguments against basically boil down to ‘make it harder for the average user to do this’. In addition to the unequal access to information, sites like lemvote demonstrate how easy it will be for the average user to bypass the imaginary technical barrier. Sure, you may block it now, but as the Threadiverse grows so will the number of sites and such that do so. Even a browser extension ala RES. Even without the whack-a-mole issue, it’s only a matter of time before somebody sets up such an utility for public access with an obfuscated instance that can’t be easily blocked.