"Ok, maybe the majority of comments aren't disgraceful, but there have been enough breathtakingly nasty misogynistic swipes that sadly just confirm for me that mostly women are women's own worst enemies."
I very much agree with the above statement.
But... after reading the summary of the situation and back a few pages from the end of the thread, I am still not impressed in the least by OP's leaving her son in the car... even when he is used to it, which is not good IMO 
Chelmsford is not far from London and we would have had the same weather today (please correct me if I am wrong). It was a VERY hot day today, especially to be leaving a baby in the car, window open or not.
My DP is shocked by OP leaving her LO in the car regularly, as am I (had to get second opinion on this). And doesn't it get MUCH hotter in a car than it is outside??
OP, it is just irresponsible full stop.
At the same time, I am sure you have had some very questionable comments on MN today, but you baited for it by posting this. Frankly I question why?? 
I hope you don't leave the LO in the car like this anymore, cold or warm weather aside.
I would just not bother defending yourself on here because it will go nowhere as people will want to get the last comment in regardless of what you say.
TBH I dunno, I still wonder if this is just someone on the wind up.
I wish you luck OP, might be time for a name change??