As a consequences of the scorched earth approach artists and creators have taken towards AI generated content, many are advocating platforms and services implement a zero-tolerance policy to the medium. At face value while this might seem an effective immediate solution to stop the proliferation of AI generated art, long term this type of thinking, of outright bans or prohibitions, won't work because AI auteurs will find ways around them; tools and protocols will be updated to recognise obfuscation technology faster than such 'watermarking' efforts can be programmed and utilised. That or they'll just ignoring any restrictions.
What artists, forums, communities, do to address the threat they perceive AI art poses
depends on the relationships creative communities want to foster with regards to Generative AI and its use. For example, as outright bans won't work, for the aforementioned reasons, so perhaps a better direction to take is to require those using AI declare their content as having been made with AI, in part or whole. This could be an obligatory policy that is 'zero-tolerant' insomuch as an individual being banned for breaking such 'disclosure' rules rather than simply for using and/or producing AI content. This punishes behaviour not products (use of AI itself).
Perhaps more pertinent to artistic communities, is education, not outright "AI art bad, human art good", rather, AI artists need to understand the direct and indirect costs AI has on their ability to monetise and/or protect their work, especially in regards to Copyright law, which currently does not protect AI content in of itself - this means any work an AI artists publishes online can, and likely will, be misappropriated and used by someone else, or AI, and there will be nothing the OP can fall back on to remedy that situation. Raising awareness of this reality may cause some to pause or at least properly consider their options with regards to using GenAI.
Following on from the educative point above, AI artists might be encouraged to fully utilise the iterative power of AI as a production tool quickly able to provide a framework around which artists can create digital collages, paint-overs, or simply a means through which artists can improve technique and skills - it should be noted that this use of AI is far more likely to fall under the auspices of Copyright because it becomes a tool within the individuals workflow, a 'filter' of sorts that assists the user towards a realised goal.
Going scorched earth with AI isn't really a battle that can be won by direct, offensive action, it cannot be stopped with ban and prohibitions, especially as its creators can implement changes faster than rules, regulations and other remedial actions can be put into place. Instead it needs to be won by highlighting its (current) systemic limitations, financial especially.
