wanting to know the meaning of the sentence.
It is a turn of phrase or figure of speech that can be used in a number of ways to show you are serious enough about something to put it into words. Depending on the tone it can be taken as sincere, defensive, or a statement of fact (among others).
You could say "I wouldn't say I would take out the trash, if I din't mean it." or "I wouldn't say I was upset, if I didn't mean it." or even "I wouldn't say I don't like gerbils, if I didn't mean it."
It has often been used as retaliatory in response to an opposing statement...
Speaker 1 "I don't like gerbils"
Speaker 2 "Oh, he doesn't mean that"
Speaker 1 "I wouldn't say I don't like gerbils, if I don't mean it!"
If it is important enough to be put into words, it is assumed it is a statement of fact; or at least should be according to the speaker of the statement.