My question involves search and seizure law in the State of South Carolina.
Background:
While my parents were out of town, I had a few people over to drink, dance, and be merry. At approximately 0200 hours, my friend and I are speaking to one another on the back porch (no music playing) when I hear someone attempting to open the gate to the backyard. I immediately stand up and approach the door to the screened-in porch (startled at the unexpected intruder) at which point two flashlights turn on and the men identify themselves as police officers being called on a noise complaint.
I immediately attempt to politely dispel any problems with their being at my home by stating that all noise would be reduced and that their presence was no longer needed. The officers approached the screen porch and the lead officer commanded me to "Calm down and take a seat." Before I followed his command, the lead officer opened the porch door, stepped up onto the porch, looked past me (noticing an acrylic bowl sitting on the table behind me) and asked "Whose marijuana pipe is that?"
At this point I took a seat, and while the lead officer looked over my friend and I, the other officer went inside my home and rounded up the three friends inside to bring them all on the back porch. From that point on, a full search of our persons was conducted and two SCHED I drugs were found in a friend's purse (arrested), I was written a ticket for PURCHASING BEER OR WINE FOR PERSONS UNDER THE AGE OF 21 (SECTION 61-4-80.), and two minors were cited for being in possession of alcohol.
My questions are as follows:
1. I am under the impression that a screened-in porch is considered 'curtilage' of my home. If this is the case, what right did the police have in letting themselves onto my porch (at which point illegal activity was discovered) when they were confronted by one of the householders prior to "porch entry"? I'm under the impression that the police had no right to further enter into my property after contact was made with them, and the reason for their being there was addressed.
2. Was their (the police's) behavior at all inappropriate (i.e. useful to mention to a lawyer) in that they did not attempt to knock on the front door (which has a cement path leading to it from the driveway in which their cruiser was parked) and instead made a B-line to the gate to the backyard (which has no path leading to it)? Like I said, my friend and I were speaking to one another without music playing. Can they come into the back in an attempt to make contact with an occupant simply because they hear voices emanating from the back? How about if they DIDN'T hear us? Does the fact that the gate has a latch (that the police reached across and lifted) with a built-in "pin and tumbler" lock affect any of this?
What I DID do: confront the officers from inside the screened-in porch -- stood in-front of the door to the porch and addressed their reason for being there -- responded politely, but urgently, to them before they entered the porch
What I DIDN'T do: give them permission to enter the porch -- open the door to the porch as they approached it -- act threateningly towards them which would have warranted a command to "sit down" -- ask them to leave
After the pipe was found, the officer then attempted to explain his reasoning for telling me to "sit down" when they first arrived. His reasons included : 1. My agitated nature (albeit, polite) and 2. The "Rage Against the Machine" shirt I was wearing gave him the impression that I might "...rage against (his) machine!"
I understand that the police must protect themselves and watch out for their own safety (and secure the area to protect themselves), but my agitated nature was due entirely to the fact that someone was attempting to enter my backyard in the middle of the night. This was NOT a party and I had no expected guests arriving later... what reasonable person WOULDN'T be frightened at any intruder attempting to enter their yard at night? If they were so concerned about safety (at a home that costs ~$200,000), why didn't they knock on the front door? Throughout the ordeal, the police made multiple comments about the possibility of us having guns stashed either in the house or outside the house and that they had to make all the moves, including, searching purses for ID, getting a pair of shoes from inside, and searching upstairs and downstairs rooms for God-knows-what.
All in all, was the police's entry onto my porch, and subsequent discovery of illegal activity, legal?
Thank you very much for any and all help provided. This whole ordeal left me and everyone involved feeling completely violated.

