The dilemma is that you consider yourself a liberal, but your parents lament at your choices and wish you were more like them. It's not uncommon for people from the same families to have very different views on politics, religion, marriage -- and even the types of food you eat and the places you choose to live. If you're in the midst of a clash with your conservative parents, take a deep breath, take time to appreciate your life, and then prepare to grin and bear it.
Make yourself financially independent -- or at least, not dependent on your parent's bank account. If you're a grown adult and you're still living on your parents' dime, then you're going to have to take some level of interference about how you spend your money and the activities you choose. If, on the other hand, you're earning your own bread, your parents are going to have to accept that your "liberal choices" are nevertheless affording you the lifestyle you choose. There's nothing like being successful in life to show your parents that your way is not so bad after all.
Set your boundaries when it comes to your home and your children. Your parents are entitled to their own opinions, which aren't likely to change. However, you can control what happens in your home. Have a conversation with your parents about what is and isn't allowed in your home -- and ask your spouse to back you up. Honor your parents' rights to watch conservative TV shows or read radically close-minded books -- just let them know that they can't do those things in your house. When there are grandchildren involved -- and not following your house rules results in them having only limited time with their grandkids -- you might find that they start complying with your rules pretty quickly.
Avoid getting into political discussions -- especially during holidays or other special holiday times. You already know that you disagree with their views. Trying to slam those views down your parents' throats can result in resentment. Ask your parents to follow suit; let them know you honor their right to view the world in their particular way -- they'll love that -- but also let them know that you want them to honor yours. If the politics do start flying at the dinner table, stay calm and remember that there are people with whom you share views -- they're just not present in your dining room.
Give a little. You might be a hard-core vegetarian who only shops at organic co-op grocery stores, while your mother might be more of the big-box shopper. Instead of displaying your judgment and resentment for her less-than-PC choices, try a little compromise. Showing that you're willing to be a bit flexible may encourage your parents to do the same.