It's not a matter of feeling guilty, it's a matter of you being in a trusting relationship. Your assertion that 'men lie' is worrying; does it follow, for you, that because your husband is a man, he's likely a liar?
That's you not being in a healthy place, whether he's betraying you or not.
People lie, but not all people. Some people 'access filth', some don't. If you don't like the idea of your partner 'accessing filth', and you think he might be, and would lie to you to cover it up, your relationship is in a mess worse than him watching porn. If you can't believe what he tells you, you can't believe the vows he made to you.
Not all men lie, just like 'not all women gossip'. The historical stereotypes aren't true for everybody, or even for most. You don't have to assume that lying is a likely part of your marriage, due to your partner being a man.