If you want to start a heated discussion, just bring up the subjects of religion or politics. People often feel strongly about one or both topics and from an early age we are taught to avoid talking about them at parties or similar events.
Religion and politics are very personal subjects and many people have strong beliefs about them. For this reason, they are considered off limits in polite discussions.
Wars are still being fought over the subjects. Many people aren't open to new ideas. They believe their views on religion and/or politics is the correct one.
Some people feel comfortable with their opinions and are threatened by opposing ideas. They shut out new ideas to protect themselves. Other ideas are not considered or considered and quickly rejected.
Politicians often have the same problems when discussing hot button issues. Many times differences in opinion lead to arguments and resolution is hard to achieve. Sometimes common ground is never found.
Political settings can bring together people who feel vehemently about their side of an issue. They are so motivated by their beliefs that they are unlikely to see the other side of the issue.
Sometimes the only way to find common ground in the world of politics is to elect politicians to represent your particular view. That way they are likely to vote as you would like when particular issues are being considered. However, to ensure that your views are being represented, you have to remember to vote. Research the politicians that support as many of your views as possible. You may want to stump for them or volunteer for their campaign to ensure they are elected or stay in office.
You may find that stacking the decks with politicians you support will aid in promoting discussions of topics that concern you. It may lead to the passing of bills that support your agenda.