It's unprofessional. Anyone that is deploying things into a production environment without extensive careful testing and quality assurance is either selling something so dreadfully irrelevant that nobody cares if it's full of bugs and issues, or is putting others lives, jobs or wellbeings in danger.
Wrong. Extensive automated careful testing and quality control can be built into continuous deployment pipelines. (Quality assurance for defect prevention has nothing to do with continuous deployment one way or the other. Many people in the software industry confuse QA with QC.)
Again, no, you are wrong. You cannot do continuous deployment and quality assurance. The entire point of continuous deployment (or delivery or whatever they call it now) is that you are deploying constantly from master.
Again, no, you are wrong. You can do continuous deployment and quality control. All of the tests necessary to qualify a particular build for release can be automated and included in the delivery pipeline. If you disagree then please provide a specific example of a test which can't be automated that way.
Quality assurance (defect prevention) activities are performed before code ever gets to the master branch.