> Who told the agent to write the blog post though? I'm sure they told it to blog, but not necessarily what to put in there.

I don't think it matters. You as the operator of the computer program are responsible for ensuring (to a reasonable degree) that the agent doesn't harm others. If you own a ~~viscous~~ vicious dog and let it roam about your neighborhood as it pleases, you are responsible when/if it bites someone, even if you didn't directly command it to do so. The same applies logic should apply here.