UBT, wouldn't a more "reasonable response from a reasonable man" have been to give the company (that you'd previously used and sufficiently trusted enough to have recommended) a call to inform them that you'd seen something that you felt was dangerous and reflected badly on their company?
I would have appreciated that if I were the company owner as it would have given me the opportunity to apologise to you, investigate the matter and to ensure that it didn't happen again.
You didn't know the circumstances surrounding the dangerous driving but there may have been at least some mitigation for it - a personal emergency etc - it wouldn't necessarily justify it but it may have been a legitimate factor that could have in part explained it. It may have just been crappy and dangerous driving of course (probably more likely).
But to publicly berate the whole company for it and to threaten to actively talk down this persons business without giving them an opportunity to deal with it seems a bit "strange" to me too.
It seems about as unnecessarily aggressive as the driving that so infuriated you in the first place - both can do a lot of damage.
When someone or an organisation at the very least scares the living daylights out of me, in an incident that could have injured me, or worse, I think it quite reasonable to react in the manner in which I did. It was neither 'strange' nor 'aggressive' to hold the company up for public examination for the actions of themselves or their employees. Irrespective of whether I had or had not had a relationship with them. AA have been made aware by SteveJ of this post and could have responded here, it is easy to join the forum, if they are not members already, and could have easily responded here for all to see, in the same way as I did. As it is they responded to me personally an hour or so ago, offering an apology for the actions of the driver, which I accept and will draw a line under the matter for me, aside from a quick response to Steve A below.