Actually the denomination of קצוצי פאה or people who cut their hair short at the temples seems to target the Bedouins and nomads dwelling in the Arabisan desert. See for example Jeremiah 25:23 where the same expression is found in connection with the nomads and desert people: Dedan, Tema, Buz and kings of Arabia. There is no indication that Israel is included in the denomination of קצוצי פאה, or any of the other nations listed in the verse for that matter. This custom of cropping the edges of temples and forehead has been attested elsewhere:
those polled, cropped at
the edges of the beard and sides of the head, are such as have the
hair cut from off the temples and the forehead, observing a custom
which, according to Herod. iii.8... was
usual amongst some of the tribes of the Arabian Desert. The imitation
of this practice was forbidden to the Israelites by the law, Leviticus
19:27; from which passage we may see that פאה refers to the head and
the beard. (Commentary of K&D)
However, there is no reason to take this as an admonition directed at the Arabians for practicing this rite, although the epithet קצוצי פאה smacks of derision (or as you would have it "great contempt") and may have been intended as a denigratory denomination of the Arabian tribes (similar to the epithet ערלים "uncircumcised" which is derogatory of the pagan nations). However, your conclusion that the text indicates that the "God of Israel was incensed with Israel's neighbors for their grooming" is a little bit far fetched. Would you say that the phrase "for all these nations are really uncircumcised", in the end of that verse, indicates in any way that he God of Israel was incensed at the pagans for being uncircumcised?
But we mustn't get carried away with semantics, the essence of this prophecy is that all the nations including Israel, circumcised and uncircumcised, will be punished for their sins, "for all these nations are really uncircumcised, and even the whole house of Israel is uncircumcised in heart."