Nixon deserved and still deserves all the bashing. One's good deeds do not counteract one's felonies, hubris, and arrogance. I lived through the awful Nixon years. One of the great lies that got him re-elected was that he was going to bring home tens of thousands of troops, which he did - and then sent tens of thousands of fresh troops right back again to replace them immediately after being re-elected.
To most of us at the time, it wasn't the lies which we knew he was telling, it was the breathtaking arrogance of defying Congress, the Supreme Court, the justice system and the will of the people who elected him, stonewalling the investigation at every turn and throwing everyone around him under the bus to try to stay in office. They were very dark days indeed, and the whole country felt tainted and dirty. He put an entire nation through hell - I've no sympathy for him whatsoever.
The phrase "Would you buy a used car from this man?" was coined about Nixon, and he didn't earn the nickname "Tricky" because he was a magician.
The system should be the way the ancient Greeks used to have, the equivalent of jury duty. One day you get a letter in the post and bang, you're president (or whatever office) for a year, just long enough to learn the ropes and enact some things, but not long enough to really screw things up or become utterly corrupt.
The desire to be a politician should bar you for life from ever being one.