The guy didn't "stop" the OP says "Immediately upon entering the parking lot, First car slowed down to a crawl". Even in their verbal exchange she didn't say "why did you stop?" she asked why he "slowed".
Surely the incline of the entrance ramp can be seen. The OP should have looked at where she was turning into before turning, or if she couldn't see it, be ready to expect anything. Just because her car is small and the incline isn't an issue, its really not news larger, lower cars will scrape transitioning from a flat road to a steep incline - the slowing should not have been such a shock.