Driving 38 vs 35 is hardly an unsafe difference...

These are machines. They should obey the speed limit.

For people learning to drive -- the first step is learning how to obey the rules. The second step is learning which rules can be bent. Let's focus on step one at the moment.

Where I'm from, at least, for people learning to drive the first thing you learn is that, if you go the speed limit, you are going too slow and will irritate everyone around you.

Driving the speed limit is never unsafe. And especially not in a residential area 35 MPH zone.

Driving the speed limit is frequently unsafe, e.g. in adverse weather conditions or unusual street conditions (like when passing an adjacent block party with lots of adults and children milling about.

The speed limit is the maximum speed limit in ideal conditions.

Driving the speed limit is frequently unsafe. I drive on highway 401 in Ontario frequently, where the speed limit is 100kmh, but traffic flows at 120kmh or above, with faster traffic going more like 130. Going the speed limit means you are going 20kmh slower than the speed of traffic, and 30kmh slower than faster moving cars, which can definitely be dangerous since accidents are more often caused by speed differential, rather than absolute speed.