When writing comedy, you need to connect with people on some level or another. Telling the truth is one of the best ways to do this.
The ‘Truth’ you are telling need not be real, but you need to pretend that it is. It has to be grounded in reality somewhere*. It has to be your own truth.
You can construct your own truth, but people have to want to believe it.
If you try and bend the truth too far, your comedy becomes to affected, and loses it’s humour, in which case it’s not funny – It’s just sad.
*The exception is surrealist comedy.