I don't get why the police forensics should not have access to a hard drive data when they have a warrant.

What's next, we should fight against the police right to enter a home with a warrant?

Seriously, people are fine with police carrying guns, but they should not have access to a hard drive because they could misuse the power?

I'd rather fight for sound rules on delivering warrants, and efficient checks on abuse of power.

Exactly. It's the old power vs freedom problem. Pursuing absolute freedom is stupid: when you increase someone's freedom at the expense of the freedom of someone else, you are not increasing freedom globally.

The freedom to harm others (physically or, in Stallman's view, by depriving them of the right to change the software they use) is better called "power", and that is not desirable in itself.