I mean this is by design? It makes pirates more likely to get malware, and thus normal people more likely to pay for MS products rather than pirate? You may think its immoral but the incentives line up.
I don't think it's some conspiracy to make anyone more likely to get malware. Instead it's that for their business model of mostly being used on business PCs where the same dozen tools are installed all over the world they can be overzelous in protection and it is what most customers want. Really, they should leave the "piracy is malware" thing in defender, it should just be off by default if your PC isn't connected to a domain or setup as "work PC".