Did you read about the copper snake, or were you taking a nap during the Torah reading yesterday?
The Israelites were grumbling, and God sent fiery snakes to bite them. Ouch. Then God told Moses to set up a copper snake on a pole; they could look up at it and be cured.
Fast forward a few hundred years, and Hezekiah destroyed the snake because people had been burning incense to it.
When a symbol of your heritage–something your people have cherished and honored for generation after generation–becomes an object of idolatrous worship, the time has come to destroy it.
You can read all about this and form your own opinion. Look at Numbers 21:5-10 and 2 Kings 18:4. Of course, translations differ, and there are some nice bits of wordplay you can find in the Hebrew, but the point is the same. If you look at the Talmud (Berachot 10b), you’ll see that the Rabbis approved of Hezekiah’s action.
Up with the Rabbis, down with the Confederate flag!
Sharing Jewish Tradition 
The copper snake references you cite remind me of what I’ve been reading, Freud’s Moses and Monotheism. Highly speculative book, it suggests two movements making up earliest Jewish religion, a Mosaic monotheism from Egypt and a Midianite-influenced cult from southern Canaan. The latter would have been tolerant of idolatry, pagan magic, and such. Hezekiah then would have been acting to put down the other trend.