Here's another "Stairway to Heaven" soundalike I bet you've never heard of:
There are plenty of songs that use this same descending chord progression. What triggers the Led Zep connection is hearing it played with guitar picking, like in the Taurus song and this one here, by Walter Rossi (a terrific songwriter who never got his due). I agree with the ruling -- it's not a ripoff of Stairway.