And with a proxy you can bypass most filters. The internet is a dangerous place. For every filter or block that comes out, eventually a workaround will follow. Its better to understand the dangers out there and learn how to avoid them. If an individual wants to get around a filter badly enough nothing will stop him. A filter is good for passively blocking content from appearing.
As for Google, set your “Safe Search Settings” to “Use Strict Filtering” that should help exclude certain material from appearing in your results.