I cannot believe there are people questioning whether or not this is a big deal. You Do Not Leave A Toddler Alone To Buy Cider. What is so fucking hard about that to understand?
I don't mean to play a trump card here, but I am a single parent to 2 v small children - 4 years and 21 months old. My husband is dead, therefore I am truly a single parent. I live in a small village with a shop about a 2/3 minute walk away. There is nothing that would compel me to go to that shop while my 2 girls are sleeping. As it is not a responsible thing to do. I have to take the bins out (thankfully not to the end of the lane anymore), but I plan it so that either the girls are out with me or that they come with me (both try and pull the bins themselves). Nappies, capol, whatever, both children would come with me if I absolutely had to go out for urgent supplies.
There must be at least a weekly national news story of a whole family being wiped out in a fire. Just about everything carries a risk: driving your car is probably one of the. But you mitigate those risks. I wouldn't leave very young children alone in the bath - how the fuck would I feel if they died while I went to answer a fecking PPI call? Or if they died when I went to buy cider at the local shop? I would have to kill myself, which in turn would kill my mother.
OP, your DH was wrong. From what I have read, he has taken this and admitted his mistake. So it wouldn't seem that it should be a deal breaker in your marriage: just a lesson learned for him.
For all others proclaiming that there is nothing wrong with leaving a toddler while popping out to buy some booze, I suggest you take a very good long hard look at yourselves and ask why you think this is the case. It is not a good thing to do and is incredibly bad and irresponsible parenting.