As a newbie with one post I really don't think anyone is prepared to sell Bitcoin via PayPal. Hell I'm finding a hard time getting sellers via PayPal and western union and I've been around for some time now with a good enough rep.
If he paid with Western Union, wouldn't that be a safe transaction for the seller?
Whoever is sending the funds via western union is the one taking the risk, either way a trusted member acting as escrow agent or bitcoins sent first would be the only way I would deal with members wanting to sell via western union that aren't trusted members of this forum..