Human rights inflation means that people think more and more rights are important for people to have and should be protected. Just like when you inflate a balloon — you add air to make it bigger — more and more rights are added to safeguard people from harm and discrimination.
For example, it used to be okay to treat people differently because of their skin color. But now people know it is wrong, and there are laws in many countries to protect people from discrimination no matter what their race or skin color. This is an example of human rights inflation — more rights were added to make sure nobody was treated unfairly.