BTW, I'm not saying that you SHOULD lend them the money... I'm just saying that there are some circumstances where I'd feel more comfortable about lending money than others. In the case of tiding someone over between the purchase of their new house and the sale of their old house, I would be pretty confident in getting the money back (yes, I've done that before) because you KNOW where the money is coming from.
On the other hand, if someone were borrowing money and you have no idea whether they will ever be able to pay you back (for whatever reason) then yes, I would consider it a gift if given at all. If they are the type to decide that rather than paying you back they's rather put a pool in, or redo their kitchen or something like that, then yes, you should consider it a gift if you lend money to them at all. If they are borrowing the money to live above their means, then I would not lend it to them... however, it doesn't make a person financially irresponsible to rely on at least part of the equity from the sale of their old home in order to close in their new one.
BTW, I don't even know that this is the situation... I'm just making a guess based on the info that the OP shared. IMO this type of loan is a lot less risky than any other type of a loan because you know where the money to repay you is coming from. Of course if they are not the type to pay you back at all, any type of a loan is risky.
Edited to add since our posts crossed: If they are buying new furniture then obviously they don't care THAT much about closing in their new house early. You're not being cold hearted at all... the fact that you are second guessing what is a wise decision actually says the opposite, your heart is probably a little too big for your own good.
Life is all about making choices and tradeoffs and it's REALLY unfair of them to expect that you will make it possible for them to "have it all" if they are not able to do so on their own.