Twitter is a public forum. What is said is said. Yes you can edit it and correct it, but anyone should be able to see your history of edits - you need to be held accountable for that which you do in public. Imagine a political leader telling his followers offline - Look at my tweet at 2pm, and then he deletes the incitement at 2:01 pm. He can deny he said it, and that it is fake news that the opposition claimed he incited his followers.