There was a study a few years ago that found a strong link between drinking black tea and esophageal cancer. It didn’t note any temperature connection, though it makes some basic chemical sense that warm or hot tea would have a greater effect than cold. That study also found that adding milk eliminated the cancer effect, but IIRC correctly did not attribute the difference to temperature. In my experience, most people who drink tea without milk just wait a little longer for it to cool down. Also, adding milk to green tea neutralizes most of the anti-cancer effect of green tea, so I tend to think the milk effect found with hot black tea is related to a chemical reaction with the cancer-causing substance, and not just a cooling down of the tea.
The milk counters the tannins in black tea. Drinking black tea straight is were you run into the chance of cancer.