Generally I am a bit careful discussing FIRE/personal finance ideas. First, there's no point talking to somebody about the 4% SWR concept if they currently eat out for lunch every day, have no emergency fund and a big car loan (learn to walk before you run). I might politely discuss with them the cost versus enjoyment/value of eating out every day as a starting point, see if they might agree that eating out less often and cutting some optional spending would put them in a better position. Secondly, as OP described, for most people if they hear about something they don't do, that might seem better but involves some lifestyle changes that could include short term self-control or restraint, they will normally reject it straight away and if pushed further go on to aggressively defend their current position, insulting you as part of it. There is unfortunately little that you can do about those kind of people in the short term, so best to leave them alone (they'll likely follow like sheep when everybody else starts doing it).
If strangers/acquaintances call me cheap or similar then I'm perfectly happy to ignore them, and do so. Fortunately all my good friends are all financially aware, and while they may not be targeting FIRE specifically they do understand the value of money in the bank, planning for the future and can differentiate between necessary and optional spending, so I can talk about big picture financial concepts with them. You can't choose your family, nor (typically) get a way with ignoring them, so what can be useful is to take the conversation on a tangent, so if asked why I don't own a house or operate as a buy to let landlord, I discuss house price/rent ratios, management fees/maintenance costs and yields on property funds: the mental maths and range of conflicting factors is normally enough to confuse them into submission, or at least allow them to admit that in my specific scenario what I'm doing could temporarily be OK (without having to compromise their general view). In short, that may be called "intellectualizing the problem" and can only be used selectively...
