I think the reason is simple. FL can't apologize. So, ML must be made a douchebag. A husband getting insecured with his wife getting attached to her ex's baby is very natural. Makers didn't build Aryan's character like that though. Had they shown Aryan being troubled earlier with him being the second choice, it would have made sense.
Aryan puts his family above others. His selflessness is only reserved for them. He assumes Imlie's obsession with Gudiya inspite of his numerous warnings, comes from her attachment to Tripathi clan (which includes AKT). The phrasing of words got wrong. Separations seems fake. Aryan giving her a cold shoulder and withdrawing himself makes better sense.
On a side note, if a baby is in danger and if I am pregnant and I see my husband running towards the baby to protect her and he is in a position to do so (logically), I will step back. I don't blame Imlie for MC, but I expect her to be logical.