what if you live in the middle of nowhere, so they can't even get close enough to see how trashy your yard looks?
For someone to see spray paint markings on my house, they've already been trespassing for over a quarter mile...
I've gotten the "I know where I'm going" comment before, frequently because of where I live- generally they're one of these categories:
1) Friends that don't have the means to take care of themselves right now, much less after SHTF
2) Friends that are afraid the city will go to SHTF, but it may be safe where I live.
3) other preppers looking for a plan B or C
I usually meet it with, we'll all need help, what can you bring to the party?
group 1 realisitically can't bring anything but labor- depending on my trust level and opinion of their skills, that may help- i.e. I personally can't keep watch 24/7 alone- and my wife/kids lack tactical skills to asses things and would be waking me up too much
group 2 must bring some kind of supplies- and preferably a travel trailer or RV for them to live in... they have means now, so I tell them to plan on what they bring- I present it as "if you just show up, we'll all die after running out of supplies", to avoid bringing up the reality that they'll likely be on their own for that reason.
group 3 usually wants to talk about what they'll bring, and may even ask what I anticipate what I would need more than anything