Horrible character being portrayed as somewhat sympathetic doesnt negate the point being explicitly made in the show that the character is horrible. Charlie himself is constantly self-deprecating, and not actually content with himself(which is why he constantly drinks, to escape that realisation) the point is constantly being made that his sleezy lifestyle while seeming rewarding at the moment is wasting and killing Charlie in the long run. Its pretty much the running gag that every aquantaince of his is counting days until it inevitably happens. Also while we're at it Charlies doesnt even have any friends(that was even the subject of some episodes) not to mention most major/recurring characters he interacts with, many of them women, are on the pair with him when it comes to being douchebag just in a different way than misogyny.

And no shit is his horrible behaviour mostly waved off, and not taken seriously -- its a fucking sitcom after all, riffled with dark humor and social satire. Lack of serious tone when you are approaching these topics is to be expected it's literally the point of that type of humor.