Air taxi Captain reported receiving a low altitude alert from ATC during an RA response that was caused by ATC misapplication of visual approach procedure during parallel approaches.

Narrative

Norcal Approach cleared us for the Tiptoe visual course 28L; and told us to look for our traffic; Aircraft Y above us; at 6;000' (we were at 5;000' and descending). I reported 'Looking.' ATC said 'I need you to see the traffic.' Both pilots were looking for the traffic. I was looking ahead of us; because that's how the SFO visual procedures typically work in my experience - ATC tells you to follow the traffic on the parallel runway; don't pass - but our traffic was above and behind us. We finally saw it; visually confirmed it was Aircraft Y. I reported the traffic in sight to ATC; and was told to 'maintain visual separation; maintain 180kts; cleared visual 28L' I read it back; but was a little confused at how to maintain separation with an airplane that was behind us. In all the years I've flown into SFO it's always been the following; slower aircraft; that maintains the separation. As the faster Aircraft Y crept up on us; and we had to start slowing to get our flaps out. We received an RA at about 2;000' commanding us to descend. The Captain asked if I could see Aircraft Y and I said 'yes; it's right ontop of us.' The Captain aggressively descended and Tower gave us a low altitude alert. I responded 'Aircraft X responding to an RA' Tower said 'say intentions' I could still see Aircraft Y and the Captain asked me to confirm I could still see it; and he was worried they were lined up with 28L; I said 'I still see it; they're lined up for 28R.'We could not consider a go-around; because there was a plane right above us; and the bay below us. We felt the safest option was to land. Tower asked us again to 'say intentions' and I asked for a landing clearance; and received one for 28L. We slowed; configured; and completed the before landing checklist between 1000-800'AGL. Aircraft Y passed us around that time. Both planes landed safely. Both of us felt we were put in a very unsafe condition due to the sequencing of Norcal Approach.Cause: ATC telling a faster plane to follow a slower plane; but giving the separation clearance to the leading aircraftSuggestions: A change to Norcal Approach policy