The common phrase is "pet hate" or "pet peeve". The idea is kind of a joke - it refers to something fairly insignificant, which you hate with the same intensity that you would love a house pet. If the thing you hate were to go away, you might even miss it. When the writer uses "pet aversion", it is even more jocular: s/he hates things in a very sophisticated manner.

pet = a favourite; a number one