1.

What does Jack think about boxing and fox hunting?

He thinks (that) boxing and fox hunting cannot be considered “arts”.

2.

Why can't defending boxing be easy, according to Jack?

Because seeing two people deliberately hurting each other in the name of sports seems barbaric to him.

3.

What does Alex think about boxing?

He thinks (that) watching two men use only their physical strength and skills provides an experience which purges our natural aggressive tendencies.