lol that you think it's not propaganda
It's advertising, I'll grant you that.
As for propaganda, what is the message? Is the message negative in anyway?
I'm sure when the decision was made to put adverts on buses, the charity thought about the publicity it was likely to get. However, that's only because people like you make a big deal about it.
Now people will be very aware of the charity itself. I imagine they will get quite a lot of donations from British Muslims who may not have otherwise known about them. Maybe even non-muslims, although that clearly isn't their target demographic.