A retail establishment simply can not win in this scenario. How much communication a specific person wants / needs from a salesperson is an individual thing. Another thing is, car salespeople are TRAINED to IGNORE "I am just looking"... because that is basically not true.
You are in a place that sells cars because you are considering buying a car. Maybe you dont plan to buy "today" but the thought that you want / need a car has entered your (collective you) mind. Sales 101 tells all salespeople to ignore "I am just looking" when someone says that, if they came to your place of business to shop.
So you are upset and not going to buy because they over communicated. This is actually fairly normal, as I mentioned, because how much "touch time" someone wants is a very personal thing. Kind of a strange reason to potentially lose 1/2 of the remaining tax credit over, but I have absolutely stopped patronizing businesses because I did not like how they communicated to / at me.
With all that being said, you got an overly eager (to you) sales person at a place that sells cars....... reading that sentence, what looks strange about that?