Sure, SETI folk are often trained in science, and rely on scientific equipment.
But...guess what?... They put forth their supposition on what grounds?
Where's their proof? Where's their evidence?
And is their pursuit or search for an hypothetical ET purely science?
Pure science?
Show me pure science, Larry?
There is always a subjective input, or nonscientific input into science.
Otherwise, humans wouldn't be humans.
And science isn't always repreducible results.
There's a gray area.
Religion doesn't have to have a Deity or what is called a God to make it a religion.
There are substitutes for that concept called God.
The Websters and Oxford dictionaries both have broader
definitions for religion than that.
EXAMPLE: In America, football is considered a religion by some,
so why shouldn't a nonsubstantiated branch of 'science' be one too?