Dear N T:

You wrote:

 A says: Harry was talking about AN EXPENSIVE RED SPORTS CAR. or: Harry was talking about EXPENSIVE RED SPORTS CARS.

B replies:

1-I hate ALL OF THEM.

2-I hate THEM ALL.

3-I hate THEM.

In this context do the sentences 1-3 mean: a-I hate all EXPENSIVE RED SPORTS CARS. b-I hate all RED SPORTS CARS. c-I love all SPORTS CARS. It seems to me that “1” and “2” are ambiguous but “3” means “a”.

1 and 2 are saying the same thing. They would both be saying the same thing as a. 3 would also mean a. 1 and 2 are being more emphatic.