Yes, do-not-resuscitate orders endanger patients, because they prevent patients from getting care when it can save their lives. DNR orders are sometimes used improperly, because then health-care providers have to walk a fine line between providing appropriate care and providing more than the patient or the patient's family wants them to provide.
If a person is brain dead or old (80+) and has a serious heart attack stoke whatever and it is determined that they are only hanging on by a thread on borrowed time and did not have a DNR signed when they were capable of it. It is cruel and selfish to have the doctors revive them, insert feeding tubes, IVs, or ventilators only to prolong their suffering because you're not ready to let go when they are. I have seen it countless times when I worked in the nursing home. Residents would be sent out with heart attacks strokes and other conditions and died on the table several times and brought back because the family insisted on it. I have seen people who were functional and independent come back on feeding tubes, become bed bound, only to aspirate on their own saliva develop pneumonia and then die weeks or even years after returning to the home moaning in pain the whole time and never getting out of bed. I have seen people lose toes, feet, and entire legs to necrosis caused by lack of blood circulation while they were coding. These are things straight out of a horror film and I've held these people's hand while it was happening to them. At times I could scream when this happened, but I didn't I wiped my tears and hoped they could hear me when I told them it would be ok. So ask yourself how would you want to live or more accurately how would you want to die? Would it be better to go in your sleep remembered for the person you were or have your family watch you writhing in pain only to choke on your own saliva so doped up on drugs you don't even know where our who you are anymore?
Do Not Resuscitate (DNR) orders are an important tool for a person with serious medical issues to control their medical care and choose if and when they are ready to die. If someone has a serious medical problem that is causing suffering and is likely incurable, it is their choice whether or not they want to continue to seek treatment or decide it is time to let things come to their natural conclusion, even if that means death. It is not for anyone to dictate when and how someone else dies, so DNRs need to remain one of many available tools, like living wills, that allow us to have some control over the aggressiveness of the medical treatment we are given in extreme situations.