Western Union is as far and if I remember correctly, a service to send cash to other countries. It is not in any sense a bank with "Girokonto" and wire transfers. It's much like Dwolla, but with offices all around the globe. Basically you give the WU guy in Germany 100 € and another WU guy in Uganda or whereever gives $100 in local currency to your folks there. So, yeah, they are probably easy to scam. Now, there is a Western Union International Bank, but until you say otherwise, I am going to assume that it's their prominent cash transfer service that was employed in this scam.

Edit: Oh, now I know what you're talking about. Yeah, that's a very common scam. Evildoers look for gullible people that want to "work from home". They send the money in a bank transfer that was phished and they are supposed to send it on. If those launderers are caught, they of course are liable for any losses, even though they might not be aware of any laundring or that it it's not a legal "job" they're doing. This forced some poor people into bankruptcy, when the phishing and laundering was uncovered and fell back on them. The people behind all this make the real profit but they stay unharmed of course. Small guys that were hoping for a new chance in life are a Bauernopfer for them.