If he lies about porn, is he lying about other things?

Not necessarily - but once someone breaks trust, it can be difficult to repair it.

Most men view pron, and many have developed crippling addictions to it (made worse by the prevalence of cell phones, high-speed cell connections, and free pron sites).

It can be difficult, if not impossible for some men to give up pron until they make the decision to do it for themselves.  Trying to do it for someone else (even a spouse/girlfriend/etc.) will generally fail.

yes all men lie about everything

Test him for other things he might be lying about.

Maybe, maybe not. I wouldn't jump to conclusions or assume anything

Probably. Men are all liars about sex.

Liars make give-away mistakes. When they make things up on the spur of the moment, they  will contradict themselves later on, when they have forgotten what they said before. Remember details  to test him.

Yeah, sure you are, expect when you do it of course.  You might want to watch this while looking in a mirror

https://www.ted.com/talks/pamela_meyer_how_to_spot...

Maybe if you would mind your own business and quit interrogating him all the time, he wouldn't need to keep lying to you!

You should care about the effects that pornography can have. 

Pornography’s Message

▪ Sex with anyone, anytime, under any circumstances, and in any way is good and has no negative consequences.

The Bible’s View

▪ “Let marriage be honorable among all, and the marriage bed be without defilement, for God will judge fornicators and adulterers.”—Hebrews 13:4.

“He that practices fornication is sinning against his own body.”—1 Corinthians 6:18; see also Romans 1:26, 27.

Pornography’s Message

▪ Marriage is an obstacle to sexual fulfillment.

The Bible’s View

▪ “Rejoice with the wife of your youth . . . With her love may you be in an ecstasy constantly.”—Proverbs 5:18, 19; see also Genesis 1:28; 2:24; 1 Corinthians 7:3.

Pornography’s Message

▪ Women have only one purpose—to satisfy the sexual needs of men.

The Bible’s View

▪ “I [Jehovah God] am going to make a helper for him, as a complement of him.”—Genesis 2:18; see also Ephesians 5:28.

Pornography’s Message

▪ Men and women are slaves to their sexual urges.

The Bible’s View

▪ “Deaden, therefore, your body members that are upon the earth as respects fornication, uncleanness, sexual appetite, hurtful desire, and covetousness, which is idolatry.”—Colossians 3:5.