Emergency lighting or no emergency lighting, pulling the passcom could happen on any train at any time. Its what, 15 minutes from Spalding to Peterborough? It's a small risk.
Small risk? That is your judgement. Someone was already ill, which suggests keeping everyone onboard cramped conditions for even longer isn't a good option.
I'm sure the plan was to clear Spalding platform with the following trains. But they should have checked to make sure those trains *could* accommodate extra bodies before turfing everybody off at a closed rural station. Its not hard to ring the guard and ask, realistically, how many extra the train will accommodate.
Do you know for certain that they didn't try it? Maybe they couldn't get hold of some of the crew due to mobile reception black spots, or that crew were busy dealing with customers. There were also trains further behind. Those ones which were full weren't the only trains remaining. There probably was sufficient capacity to clear the vast majority of the crowd had things gone to plan with a not unreasonable delay.
The problem is that the train had to go back north for attention. Do you keep everyone onboard and delay them further, or do you detrain and try and get following services which are already stacked behind to clear them? You have a short period of time and you need to make your decision.
Without the idiot throwing the brick, I doubt so much faff would have been made out of this issue.
Control shouldn't be de-training without a solid plan for dealing with the consequences, unless its an emergency. A shrug of the shoulders and a coach three hours later is not a plan.
No plan is 100% foolproof, and who gave "a shrug of the shoulders and a coach three hours later" as the first option? Sometimes **** happens in life and things fall apart in a way which cannot really be foreseen.
The brick didn't help but the brick wasnt the problem: those trains didn't have room for extra passengers anyway, which is why they sailed through Spalding without picking up the stranded passengers.
Were there not further trains behind the immediate few following? Look further back. Had the broken window incident not occurred, and control had sent a train full of pax back north when they all wanted destination further south, I bet I'd see outcry on this forum questioning why they didn't detrain at Spalding and allow the trains behind to pick them up.
Your hyperbole and earlier calls for heads to roll just shows how little you understand how things work and how fond you are of knee-jerk reactions.