There are two items to address here that are actually quite independent of each other.
Can anyone become an anchor?
Yes, anyone can become an anchor on the network itself - the technology doesn't do anything to verify you legally can hold funds that are represented on the blockchain, just as there's nothing built into HTTP(S) that prevents an illegal website from being run. The main mechanism that exists is that each Account has to trust assets from an anchor - if you create
SCAM_COIN tomorrow as an asset issuer and say it represents USD, people have to explicitly trust that you'll actually pay them out.
However in reality, there is a lot of regulation that currently exists around money operators in various countries throughout the world. Just because one puts money on the Stellar network does not mean they are outside of a country's jurisdiction around what it's doing.
How are compliance fields validated?
Notably, the compliance protocol is for other servers to communicate with each other, and it mirrors how this works in the traditional banking system. While a bad actor may be falsely representing itself, another anchor using the same compliance protocol can mark another organization as dubious, and the user themselves has the ability to not trust any tokens from the organization.
All in all, the network itself has the ability to communicate with others about whether someone has been a bad actor, and news published off-chain is often valuable for users to revert trustlines and not accept funds from bad sources. Also, because the blockchain is public, analysis can always be done on transmitted funds between entities in order to determine illicit activity.