Few points here
1. GSTQ is a terrible anthem, there are plently of better alternatives
2. GSTQ is not the official anthem of the UK (we don't have one)
3. Liverpool is not a royalist stronghold and dislikes the London centric government (with very good reason - Google "Liverpool managed decline")
4. We never used to have to piss around singing anthems at the FA cup afaik, this is a Yank import
5. Chelsea fans booed the silence at the Hillsborough memorial