We have been told that Balaam is a villain. In this agadah, he is compared to cheating moneychanger.
And Goc came upon Balaam, whosaid until Him: "I have prepared seven altars." [...] Balaam was like the moneychanger who gave false weights. The chief of the market, becoming aware of it, asked the moneychanger, "Why are you cheating by giving false weights?" The latter said, "I have already taken care of you with a gift sent to your home." So too Balaam.
We know that much of the specificty of sacrifice laws is designed simply to set apart the practices of the Israelites from their neighbors. No less than Rambam, corroborated by archaeological evidence in the 20th century, asserted that the prohibition against meat and milk (don't boil a calf in its mother's milk) is designed to keep not from eating cheeseburgers, but from participating in a particular pagan ritual where a calf is literally boiled in milk from its own mother's udder.
The point isn't necessarily that the pagan practice is wrong, but that it is wrong for Jews. We are to be set apart through our unique ritual practices.
All of that being said, I prefer to envision Balaam not as an evil man, but as an unaware man. He clearly has a relationship with God--not everyone talks to God with regularity that Balaam does. Indeed, the text describes him as a foreign prophet. A prophet! Is he a prophet of some evil foreign god? Clear not, given his aforementioned relationship with our own God.
Are his seven altars then to be interpereted as some evil pagan machination? No. Though not a Jew, he's also, by definition, not a pagan, given his relationship with God. Is it evil? No. He is unaware of the special nature of the Jews he's been sent to curse and he's baffled at God's insistence that he cut it out.