You can be sincere and still be stupid.
I like to have strong opinions with nothing to back them up with besides my primal sincerity. I like sincerity. I lack sincerity.
Sincerity may be humble, but she cannot be servile.
Frankness is a jewel; only the young can afford it.
A sincere compliment is always grateful to a lady, so long as you don’t try to knock her down with it.
A little sincerity is a dangerous thing, and a great deal of it is absolutely fatal.