How do you ignore family gossip?

There is so much gossip in my family. My parents are still together but my father is so negative. all he does is judge and gossip about other people's lives even his own children! I have an extremely distant relationship w/ my father( I don't address his presence)so whenever I visit my mom,he makes comments under his breath.My older sister is even a worst gossip.She comments on people in such a negative way it's very condescending.I don't like to visit at all because I feel a stale atmosphere in her house.When I converse with my Mom alone my views are completely different from theirs. Then, I find mom agreeing with my opposing views but,they always come back and before you know it shes sucked back into their gossip. Without being rude, how can I tell my Mom that she needs to stop feeding into their bad habits?or How can I find a way to ingore it? It's starting to bug me seriously. I found that nothing is solved from this.