I really have seen people raising stuff like a FD here sometimes, or even A8 thinking he can get value.
It's not like he's at a level where he's doing this as a bluff.
Maybe his game is at a level he does this as bluff.

I know it's not the whole story (position, river plan, no reads, etc), but it's 6,50 in a 17,50 pot to call;
Board: 3h 8s 7d 3d
Dead:

equity win tie pots won pots tied
Hand 0: 35.140% 19.41% 15.73% 111 90.00 { 8h7s }
Hand 1: 64.860% 49.13% 15.73% 281 90.00 { 88-77, A8s, A3s, K3s, Td9d,
I play PS 50NL games and I wouldn't think all to long before calling really. People do so much weird stuff in this game that I've decreased folding decent hands to suddenly nut repping lines.

But I could be very wrong and the others are way better than me anyway, so probably listen to them. And calling does leave you in a very tough river spot where your mistakes could be large.