So i've reached the Elizabeth dane level, and the Prince says that I shouldn't kill any police officers. That makes sense, since you lose humanity points if you do kill officers. The only problem is, it's impossible for me to avoid combat with the officers (i'm a Brujah btw). I can't sneak past them since the officer always sees me and I can't convince the officer that i'm a good guy. I've tried reloading some saves and saving up points and putting them into stealth/persuasion, but none of them are high enough to avoid combat. What can I do? I don't want to kill the officers since I lose humanity. Should I just kill them all and save up points to restore humanity?
If you can't use social skills to pass the first officer that comes up to you, then I'd just say "fuck it" and not worry too much about avoiding the inevitable slaughter.
Slaughtering everyone lets you see parts of the game you probably wouldn't otherwise (social characters with even basic stealth will only need to enter a few rooms in the ship to complete the mission, making this really easy for them).
I wouldn't worry about investing points into humanity, unless you find yourself frenzying a lot. You can up this for free a number of ways - usually by completing certain quests in certain ways, but also via dancing in a club for about five minutes (just start dancing, then wait until you get the +1 humanity notification - can be done once per club).
The only truly bad thing about the slaughter is the Prince won't be too happy, which means that unless you can suck up really well, he won't give you a new Haven (so you'll be stuck with your Santa Monica one). I'm not sure how high you need your persuasion to convince him, but if you couldn't get past the cop via talking on the ship, then it's likely too low to convince the Prince in this case...