Prwong said,"if you mean by 'charitable faith' charity which you get because you have faith, which is fine' and then '...spreading your faith as a kind of charity which is clearly useless.'.
IF your faith is TRUE and you KNOW it, that can be as usefull as teling people about lunar rills, for example. Certainly interesting. Lunar rills testify to the glory of the Creator. In other words they are cool and that coolness is evidence of a Creator.
IF your faith helps you have charity it makes sense to spread that charity, ie. by spreading your faith.
All 'faiths' are not true so you have to be carefull. So I agree. Merely spreading your docrine MERELY because it is your doctrine is clearly uselss except to the exten that it lets others see your position which might be interseting like lunar rills or a perspective on reality which you could not otherwise get. I.e. like a fantasy story gives a perspective.
It might be true though you don't know it.
Spreading a false-'faith' like Communism might actually be harmful. Certainly C'ism was/is. Spreading atheism, though, false and therefore harmful from my perspective, has to be tolerated by me because I need to see into the Atheitic mind to 'baptise' it through faith. But I have to admit that to be objective or even have faith wrt(With Respect To) it, I have to consider that 'I am wrong', if only to see atheistically, etc.