Not, this is a common problem in the beginning of any dementia. The person with dementia typically does not realize they have a problem. It is a trick of the demented mind that allows them to believe they are fine... the rest of the world has just gone crazy around them. It is a rare case when you can convince the person who is having behavioral issues and memory loss to the point that others see it that there is something wrong with them.
Many spouses deny there is anything wrong. Dementia is a scary diagnosis that can and will turn your life upside down. There are negative stigmas attached to mental issues that bleed over into dementia diagnosis. There is the negativity of nursing homes, losing independence, and the images of a low decline. Symptoms come on slowly over years. Those closest to the loved one adjust with the disease and are sure they can deal with it. This can and will continue until something happens that will shake up the status quo.
The doctor is right. Because of all the new HIPPA regulations that protect a person's privacy they are forbidden from discussing anything related to the patient unless you have been approved by your father. I HATE this law. I know it's intent but it prevents us as children, who have pertinent information, from being proactive in helping our aging parents.
If your Dad become violet you can call paramedics and let them take him to the hospital. This can backfire because Mom will vouch for Dad and Dad won't remember his violent outburst but react calmly when strangers are there. You can call your local department of aging or social service. You can report the situation and have them investigate. If it is critical then they can insist on action being taken. But once again that can backfire if Mom and Dad swear you are the crazy one. Your best bet is to do what you can to get Mom to take Dad to the doctor and request a MMSE. Bribery is an option. Don't be beyond begging. I convinced Mom to go by brow beating her until she agreed just to prove me wrong
Are there other children that can be helpful? But if Dad does have a violent outburst that is dangerous, don't sit by but call for professional intervention.
As far as your Dad's status, if it is dementia then there is little they can do to make it better. The medications available today do not improve their cognition. It may slow it slightly in some patients but that is not a sure thing. If it is not dementia but on of the other conditions that can mimic dementia but be reversible it would be a shame if he didn't get treatment. But there is no way to know unless he gets a complete medical work up. NPH mimics dementia but is accompanied by a shuffled gait. A brain shunt to relieve the pressure on the brain can reverse the symptoms. There are brain tumors that can also be treated as can many other metabolic problems.
Have a heart to heart with Mom and don't take no for an answer. Ask her if she could live with the knowledge that his condition could be reversed. I'm not beyond blackmail! Tell her if there is nothing wrong there there is no fear in going to prove her right. Ask her to do it for you and your peace of mind. Play on her sympathies if necessary. She is your best bet. If the answer is no then continue to point out irrational behavior on Dad's part. Help her see that there is help available for her. Assure her that you are there for her and your Dad and only want the best for both of them. Solicit the help of other family members, friends, clergy, or anybody else she will listen to. It will take time and patience but keep at her. If the situation deteriorates and she is not going to to be helpful then go through social services. If the situation turns critical call 911.
I truly feel for you and know where you are. I wish for you that she will see and Dad will get the help he needs. Please keep typing. Many of us have been through this and I am sure others will chime in. Just know that we are here for you....