Paradigm shifts are rarely brought about without a fair amount of resistance; whether in the realm of science, as was the case for Galileo, or in other areas such as with civil rights. The explanation for this is rooted in the nature of paradigm shifts: they represent a fundamental change in the assumptions underlying a certain sector. Each area of knowledge is built upon a certain set of assumptions. The concept of slavery and segregation in the USA for example was based upon the assumption of white supremacy. Most revolutions target these premises. As history shows, people find it very difficult to radically change their beliefs and ideologies, which is exactly what a paradigm shift requires.
In Galileo’s time, the geocentric model of the solar system, with the earth at the centre of the universe, was the foundation of not only scientific but also theocratic belief. This presence of the church and religious values in the area where Galileo (amongst other scientists such as Copernicus) was attempting to re-educate people made his role in the scientific revolution a lot more difficult. In admitting that the geocentric model of the earth was flawed, the Christian Church would itself be undermined and its other fundamental beliefs would be called into question. This meant that any efforts to disprove the geocentric theory were heavily resisted and equated with impiety.
This situation can be likened to modern America. One very controversial issue nowadays is the issue of gun laws, and whether they should be restricted. Outside of the US, many people do not understand why the conflict is so important (and simply resolved by a stricter regulation of guns, as has been proven effective in other countries). The fact is, however, that the right to carry arms is included within the US constitution, which itself lies at the heart of American law and governance. A change to the gun laws would seriously undermine the constitution. It would prove to US citizens that the constitution requires serious amendment and change not only in the sector of arms but also in other areas, and that it is outdated. The fact that the issue has become so high in profile makes it even more difficult for conservative politicians to relinquish this very important point.