According to your assessment here you're an accessory to a crime - a willing and necessary participant. You said (hypothetically) you downloaded it, but that distribution should be illegal. Distribution and reception are linked, you can't get it without the distribution.

Demand for distribution fuels the supply.

I absolutely would maintain the illegality of ownership of some types of information (mitigations aside) - child pornography, imagery of rape or assault are obvious ones.

Freely allowing the supply and acquisition of details on making nukes is fine, because acquiring the components is difficult and can be controlled.

My quandary is that I want to be liberal to allow curiosity and educational intent to be fulfilled; but realise that there are elements who abuse the free acquisition of information that enables great harm (how to make a fertiliser bomb, how to make ricin).

The law for all it's flaws is ultimately a practical discipline, not abstract logic. Unless you're against all laws in general, which is a thing for some people.

(It should be pointed out that it's not been shown that this would actually be upheld by the courts).

You might be quite right in that no information should be illegal to posses. That, however, does not make it so. There's plenty of information that is illegal to posses. The fact that you don't like it doesn't make it less so.

Consider your argument with respect to privacy and data issues - obviously possession of information can be in and of itself harmful because it can be something that other people have a right to restrict your access to.

And how does one come to possess information without creating or receiving (distributing) it?