The Gaians are like Green Peace. Only with guns and a small bit of training how to use them.
Anything that upsets the "natural balance" is wrong, evil, and must be stopped. Terraforming isn't -just- taking lifeless rocks like Harris and making them livable. It's taking any bit of land, dead rocks or not, and making it livable for humans, current ecosystem be damned. That planet off in Omicron Alpha? Or the one in that huuuuuuuge Omega system, next to 49? Those are also planets that could be terraformed. And the Gaians would be just as angry then.
Besides, Harris isn't going to be a big eco jungle world. It's a tourist and mining planet, meaning lots of construction, and -very- little in the way of nature. Whatever that may be.
This is the real true story of rock and roll; it was not about anything more then, how to live your life, as a gangster, in sartorial splendor, and turning the world into a place where normality would never return again...- Malcolm McLaren