Other reputable organizations like the ACLU also support decriminalization without thinking about issues of increased demand.

The sounds like you want to think about the issue of increased demand because you already made up your mind about the issue.

I have no idea how your comment relates to anything I said.

I think the ACLU positions is that even if there is increased demand and thus more production the harm that it causes doesn't outweigh the good of legalisation. Arguing such a position however needs analysis of the good that you create.

I think that's a fair summary of their position. I (and I think they) would defend the good of legalization as keeping the government from looking through people's private computer files and sending them to prison for years based on what's there. Another is avoiding the anxiety a lot of people feel constantly wondering if some download they made might have a bad image in it that they're not aware of, or there's something in the background of a shot they didn't notice, etc.

In contrast, the good of reducing demand is a long, tenuous, and indirect chain.