There's a big difference in lying and not telling the whole truth!

Eddy got mad at Sean for lying about Emily being the daughter of the wealthy businessman who was trying to destroy their town. In my opinion Sean didn't lie about anything he just didn't explain the whole history about Emily. Emily should not have been judged just because she was the daughter of the businessman especially when she went out of her way and risked a lot to be part of the mob. Humiliating her in front of her father like that when she was only trying to help the mob and the town was wrong and was a huge slap in the face to her. I definitely think Eddy over dramatized the whole thing and the revenge he did to get back at Sean was totally unnecessary and stupid!