You are not allowed to say that! You may think he is, therefore it is OK to say " I THINK you are a lovely person" . Hope this helps, in the words of some long lost poster !!
Evidently one of the old refs tells a story,when Rodney Marsh said to him 'Ref,if i said you were a lovely person...would you send me off?..the ref said yes...so Marsh said but if I think you're a lovely person will you still send me off? the ref said no...so Marsh said 'well I think you're a lovely person'....very amusing IMO