Well…It’s a long story, really…
The short answer is, no; I’ve yet to set foot on German soil, let alone Hamburg (there’s time…). I support FCSP for their political, ethical, moral stance, with football as a secondary consideration (which is probably a good job at the moment).
But, since you ask, the long version:
I grew up following Liverpool because my dad did (I say ‘following’, rather than ‘supporting’, as I’ve never really been one for going to matches, so most of what I saw was on TV). This was in the glory days (I was 8 in 1975) of 10 League titles in 15 seasons and 4 European Cups in 8 years (interrupted only by (get this!) Nottingham Forest (twice), Aston Villa and Hamburg)… of Dalglish, Souness, McDermott, Hughes, Heighway, Keegan (just typing the names sends a shiver down my spine). Then through the much more frustrating 90s (but they were still playing great football) with Fowler, Barnes, McManaman, Redknapp, on into the 2000s With Gerrard, Carragher, Hyypiä… For all the glory of the 70s and 80s and the great players of the 90s, that comeback in the 2005 Champions League Final is the football memory that almost brings me to tears.
I slowly started to lose interest over the following 10 years. The Premier League had held little interest for me since Blackburn Rovers (my hometown team and managed by Dalglish at the time) had won it; it was all becoming about ‘The Big Six’ and, even though Liverpool was one of them, it just became uninteresting; increasingly about money and just not something I could care about. Once Carragher and Gerrard had gone, I just stopped caring really; didn’t feel like I had an emotional attachment to the club any longer.
So…
I’d been aware of St Pauli as a ‘brand’ for many years from seeing it on cool T-shirts, caps and badges with the skull & crossbones, but didn’t even realise they were a football team; just thought it was a punky / biker thing…
I got seriously into The Gaslight Anthem in 2009 and started to think that the skull & crossbones banner that formed their stage backdrop looked kinda familiar… Then I saw a photo of Alex Rosamilia (their guitarist) wearing a St Pauli cap and made the connection. I Googled around and found out what they stand for as a club, and that was that, really…
I’ll happily support any team that is anti-fascist, anti-racism, anti-homophobia, anti-sexism, anti-discrimination, anti (as much as is pragmatically possible)-corporate involvement in football, whose fans go and pick up refugees and take them to see a match (amongst a great deal of other charitable work)…And, let’s face it, they come onto the pitch to ‘Hell’s Bells’ and have the skull & crossbones on their corner flags! What’s not to like? Apart from the football, obviously 
Also, there are quite strong links with Liverpool:
‘You’ll Never Walk Alone’ is pretty much their anthem, and they have a strong association with Glasgow Celtic (probably mostly as a reaction to Hamburg FC’s association with Rangers).