Speaking from experience ... What Konishikawa's thinking is pretty realistic. For someone who is logical but has weak emotion control, the moment you know you're wrong, you will take another approach drastically. Did A and everything was burning, let's do Z instead. You know that there's a series of alphabet before Z, but ANOTHER FAILURE is not an option. That's simply not logical. It's like a science experiment, if you know A is wrong, then don't let B that is still close to A as a factor in the equation. C, D is still close, ah fuck it, we'll take Z. Being strict is the one that led Konishikawa's downfall, so rather than lowering the strictness, he chose to erase it completely.
We might think that he should know that he's doing something wrong right now, but where's the consequence? His work is still going well, his relationship with others, co-workers and the chef alike, is still good. Clearly what he's doing is correct, because it brings results. Yes, he's suffering, but he'll just take it as an old wound, a burden he has to carry to be a reminder of the wrong he did in his marriage. And he'll carry it to make sure he won't forget, thus he won't repeat the same mistake.
That's how the "I do not have the right to love" come. He tried once, failed, made his ex-wife miserable. Why would he try again? This is somebody's life, you can't just ... taking another chance to love, to see if now you'll succeed. What if he hurt another person?
Adult doesn't mean mature, doesn't mean completely mature in all aspects. Konishikawa maybe an adult, a senior, but he still has rooms for maturing, especially about his own emotion. I hope the mangaka can do a good job portraying his grow... and also Misato!
Earlier chapters are just fun bit about liking your boss, and now we have heavy stories.... Not complaining though!