Why do some people get so mad when I tell them they may not enter their credit card number,  the card must be present or no sale?

No place takes only the number when you're there in person. 

They get mad because they can't get away with it.  With all the stolen credit card numbers, businesses have to enforce the rules, and if people get upset, too bad!!  It's a real pain when your cc# gets stolen.  Businesses need to be on top of it, yet even places like Walmart do not have the best security measures.

That is the exact reason most places don't allow the number to be entered if the card isn't present. I had a card that was active for 4 years that I used often and the strip on the back was worn out so bad it wouldn't read. I had to enter the number manually or allow the merchant to do it. The card had to be present, in hand, or they wouldn't do it. It's a security measure to prevent theft and fraud.

Why people get upset when they don't have the card? People are stupid. There are also thieves and other types of bad people out there in the world among us. 

Not only requiring having the actual card, I'd also require a photo ID since there is no PIN to ensure they are the cardholder.

"I'm sorry, but the credit card company and store policy requires that you have the physical card handy.  This may seem silly to you, but I can't change it.  If you'd like, I can put your items aside until you can locate your card.  If you're still upset, I'll have the manager come to speak to you."

They are angry because you caught them in their scam.