"Both Seals and Crofts insist the song’s message was, simply “don’t take life too lightly,” to stop and think before going through with an abortion."
Also as I noted - Their new found faith was probably the biggest reason for their fame and stardom to wane - also noted in your link.
" - hey’d managed to work many of the key tenets of the Baha’i faith into their lyrics, and after every concert they returned to the stage, house lights up, and held informal “fireside chats” about their religion with whomever felt like sticking around.
That seemed to be enough. Proselytizing was and is a no-no for Baha’is, but Seals and Crofts had found a safe middle ground, where they could express their beliefs, and still have hit records."
The song may have been the beginning of the end of their success but it wasn't because of that one song or the album - It was because of their changed religion. The religion had taken over their song writing and their fandom - noted in your link.
My thesis isn't that you were wrong because that's what they did, they risked their popularity in a big way - I simply saw their fame and celebrity slowly disappear because of their religious issues and the proselytizing.