He has been open about having a stutter well before his mental ability ever came into question. Acknowledging the man might be struggling with his stutter (very possibly due to his old age) is not in the least bit insulting. People taking clips of what appears (to many of us) to be him stuttering and labeling it as dementia and being unfit for office and mocking him for it is incredibly insulting. I dont even necessarily disagree that his mental ability is probably in decline. But blanketing every issue the man deals with as dementia or whatever other term you want to use is not constructive. Both things can be true at once.