Honestly, I think porn is not inherently dangerous, but it can be a part of a dangerous lifestyle. You said no half baked theories, but to me this is simple truth in addiction and dopamine. In a nutshell, when you indulge in something, it brings a greater reward to your brain due to the “limited” nature of said indulgence. What happens if you consume an indulgence everyday? Naturally, your brain will build a tolerance to the indulgence and you no longer recieve a similar reward for indulging. This leaves your brain in a craving state as it still has a sense of the previous “high” from that first indulgence. Therefore, you begin to either A: seek out higher-rewarding indulgences (aka more porn and of different variety) or B: you indulge with other non-porn related substances (You can also have both possibilities simultaneously). This behavior in caving to indulgences sets a bad precedent, and can causes trend downward of losing self control and engaging in more and more degenerate indulgences. In essence, porn is not bad, but often leads towards more lenient behavior in regards to abstaining from degenerate behavior. Again, this is an abbreviated run down of what I know and without sources, but is consistent with studies pertaining to addiction, self control, and porn.