A photoshopped picture of the band with Trump originally appeared on the group's Instagram page last Friday (20Jan17), the day of the new U.S. President's inauguration.
It was subsequently posted again on Tuesday (24Jan17), alongside a caption in which Araya revealed he had been the source of the image.
"Believe it or not this picture was posted by me Tom Araya on 1/20 (20Jan17) cause I thought it was funny," he wrote, also questioning why the original post had been removed.
Araya's bandmates have now expressed their displeasure with him for using their official Instagram account to post political messages.
"As was verified by Tom, this was his post, is not something the band would have posted if asked, and does not belong on a Slayer social page," the group tell Rolling Stone. "We all have our personal opinions, some of which we have voiced in the past, but Slayer has never endorsed any political party or any candidate, and the band intends to keep it that way."
In his message revealing he was behind the Trump photo, Araya also slammed those who responded with criticism of the President, calling them "snowflakes", a derogatory term used by right-wingers to mock left-winger's alleged over-sensitivity.
Despite Araya's backing, Trump, who has been embroiled in a series of controversies just days after taking office, is largely opposed by the music community.
Acts including Gorillaz, Cold War Kids, Joey Bada$$, Death Cab for Cutie, and Lily Allen have all released songs protesting his elevation to the presidency.