dont mind blue flag messages when i deserve it but thats not very often.
what does pee me off is the blue flag let me through "spam" you get when they are closing so slow that it takes them almost a lap to catch you. especially on ascot club when apart from the 2 hairpins unless your a complete dimwitt you arent probably going to hold them up, i try to time it so i can pull wide at entrance to the hairpins and let them through without slowing them but it must be said that part of the skill of leading a race in real life is judging your speed so you catch a backmarker at a place where you can pass them, i.e. its better to be a touch slower before a bend and then at full speed through a bend so you can pass on the next straight rather than being held up through the bend, and letting the car behind get a run on you, or even worse trying a desperate lunge to pass the backmarker from too far back befoe the bend.
one final point
Manners help a lot, ask to be let past, don't demand it and if you can bind a "blue flag get out of my way" type message to a key, you can certainly do the same with a "thank you :-) " to use after they have let you past !