The fact that you or anyone else gets 'tired of' hearing such comparisons or your only reaction is 'you are saying he is exactly like Hitler in every way and would do exactly what Hitler did immediately blah blah blah does not negate the comparisons.
Like everything else in life the comparisons run along a spectrum. If someone exhibits even the slightest resemblance to a past figure they are fair game for parody, and no comparison is meant to go from zero to 100 miles per hour. But many can only see either/or, us/them, black/white, good/evil.
The world is multifaceted and complex and the fact that you or other people don't understand that is sad but irrelevant really.
In the end it is good to have a list of the worst humans that have ever lived, and as soon as you see even one or two or their traits being manifested in someone currently seeking power, then it is wise to raise the red flag and say "uh, we've seen this thing, even if it's a little thing, before. Let's keep an eye on this, it may be nothing but...".
Comparing Trump to Hitler isn't "parody," it's stupidity
Notice no one is comparing any of the other 17 candidates to Hitler or Mussolini or any other tyrant of the past.
Hmmm.
Oh, that makes it OK then ...