Inlaw Opinions

About two months ago, my husband and I had dinner with his parents. The conversation over dinner turned to a political discussion about global warming and fracking. Through most of the conversation I bit my tongue, but then I finally had to say something because I worried that my silence was giving the impression that I agreed with the positions being presented. My in-laws live in a very large home and I suggested they are being a bit hypocritical living in such a large home that they heat while advocating that fracking should be banned. I really thought my comment was respectful, but my mother-in- law felt insulted and left the table. My mother-in- law has told my husband that she felt insulted and has not invited us to dinner since. We used to have dinner with my husband’s parents a few times a month. My husband wants me to apologize to smooth things over. But I don’t think I said anything that I for which I should have to apologize. Should I apologize? Please add any advice in the comments section.