Conversation:

Ok, I agree with everything, but if you put in the milk first (so as not to scald it) don't you then lower the temperature of the water that you are going to put in?

Indeed, but as you have already made the tea in a teapot the tea has already brewed and, as such, the danger period is over. Once you are actually pouring into the cup, the tea-making process is effectively over.

If, however, you are making tea directly in the cup, always put the milk in after the tea has finished brewing and you have removed the tea bag. It makes all the difference in the world.