Earth Crisis had a huge impact on both the hardcore punk music and its ideals. MetalSucks said: "For anybody who was not in the hardcore scene back then, it is hard to describe the impact they had or how controversial they were. You either loved them or hated them for bringing both metal and veganism into the hardcore scene". Sociologist Ross Haenfler stated in The Vinyl Factory that "Earth Crisis became the face of straight edge throughout the 1990s" through "the convergence of 'radical' animal rights activism, a more aggressive 'metalcore' sound, and hardcore crews", becoming "one of the most controversial bands in the scene's history."  Their albums Firestorm, Destroy the Machines and Gomorrah's Season Ends were particularly influential for the emerging metalcore genre. According to Andrew O'Neill, "Earth Crisis inspired a much more heavy metal sound in hardcore" and "the distinction between the two [genres] started to crumble" shortly after those records were released.  To a large extent, Earth Crisis was responsible for the rising of vegan straight edge militancy in the mid- to late 90s, when veganism was rarely present in mainstream culture. Haenfler said that, while "earlier straight edge bands advocated vegetarianism - for example Youth of Today, Insted and Manliftingbanner", Earth Crisis "made animal rights (and environmentalism) central to the scene" as a "self-described 'vegan straight edge' band", "inspiring thousands of kids to give up animal products entirely." They also spawned many activists in the scene because their message "imparted the sense of urgency in a way that nothing else that ever come before had", according to Peter Daniel Young.  Some of their songs went on to be considered by some as anthems, such as "Firestorm" for straight edge and "Ultramilitance" for eco-terrorists. They also drew major media attention, having been featured and interviewed by CNN, CBS and The New York Times, while lead singer Karl Buechner was invited to address the Congress about teens and substance abuse.

Answer this question "how did they influence hardcore punk music" by extracting the answer from the text above.
O'Neill, "Earth Crisis inspired a much more heavy metal sound in hardcore"