How can I make my boyfriend feel safe being honest with me?

Hey- Honesty is a two way street. Just talk to him. I was having an issue similar to this with my guy and I let it fester until I completely blew up at him, granted it worked for us and our communication is better now, but you don't want it to go that far. Sit him down, explain how you feel about what you read and how its making you feel. Don't accuse him or blame him just let him know the situation is bothering you, if this kind of thing doesn't stop, it's over.