Both of them are. It is reasonable to expect that sampling classes that are scheduled at the same time will be acceptable. However, it's not something students are entitled to. The proper way to respond to such a policy if you insist on responding is to explain your situation and ask the the professor revisit his policy for the beginning of the term in the future.
Sure --- the professor might also just be tired of getting attitude from mediocre students. It's never the A students who show up late and then complain about getting in trouble for it :-)
The professor overreacted, to be sure. And probably spent too much of his own valuable time on a student who is likely not worth it. A, "Thanks for the feedback." would have been better.
Such students may not be "A" students, depending on how the class is graded.
When I was an undergrad, I had a couple of "A" performances (in one case, I was among the top 3 students in a class of about 150) marked down to "A-" due to attendance/pop quizzes ("statistical sampling of attendance").
I tend to agree with you. All the professor had to reply was: "Sorry, I find it really hard to teach when people walk in late, so that is the reason for the policy." There was no sense of humbleness, or trying to see any alternative point of view on the part of the professor at all.
