actually, i think that DD says that in a funny way

, just like he's making some irony to the fact he was taken his titles

...
About the theory on Percy, 8) if his spying for the order, he must be an excellent actor, cause he must be deceiving his own parents.

It's said:
Page 68 wrote:'(...) every time Percy's name's mentioned, Dad breaks something and Mum starts crying,' Fred said.
And I think Mr Weasley wouldn't start breaking things every now and then (they're not the richest people on earth, right?

). And Percy'spersonality is always the same in the 5 books (i think). If you know what i mean

... His personality is perfectly adjusted to that sort of argument with his father ... (little evil, that boy...

)