I'm confused, mnemonic pharse isn't immune against malware or viruses, why you're linking a hack because of malware or viruses and the security of mnemonic pharse? it's similar like saying why mnemonic pharse can't protect against $5 wrench attack.

As a community, we can't since the only one who can freeze that coins are depends on each creator of the coin or if the address is come from centralized exchange, the team of that's centralized exchange can freeze the account.