Sister in law text me saying my in laws hate me?

How would you respond?
Apparently my in laws have disliked me since they met me at 15... That's 10 years! I was an honor student, played sports, and worked in high school. I was very mature. I now work full time and am still in college and we have a child together... She texted me saying they view us as the family screw ups but we are always welcome at her home because she loves us... Obviously I was offended and told my husband my son and I will not be going there anymore for family functions because that hurt a lot. 
How do I handle this with my husband's parents (specifically his mom)? I won't walk into her home and approach her with this; I wouldn't want someone coming into my home like that. But I refuse to go over there for the holidays because I don't think I can bite my tongue and out of respect for my husband it's best I stay away for now. 😡
My sister in law is 36 and definitely not a drama person. I think she was actually being honest with me because I told her I felt like sometimes I'm given the cold shoulder and she said "Hun, I don't want to upset you but you can't let it bother you, they've felt this way for a while and that there have been better options for my brother. But they don't realize the happiness and how much you mean to him."