Er, I read through the article and I'd agree with Snopes on this one. They present a pretty good argument. If you change the claim to 5/6 it becomes technically correct (the best kind of correct!), but the nuance that Snopes presents in the article is extremely compelling for why it is mostly false. Three of those 5 impeachments didn't even make it out of committee to go in front of the house, they were only introduced (and any rep can introduce anything crazy they'd like, including articles of impeachment) and one of the impeachments was Nixon which had bipartisan support.