The bolded is an attitude that I will probably never understand. Would it be immoral or wrong not to work if one had a billion dollars sitting in the bank? Is is immoral or wrong not to work if one is a retired firefighter with a pension?
I suspect the thought process is not that it's immoral not to work, but that it's immoral or wrong to accept "free" money from a government entity. Which is also an odd argument unless one is also ready to argue against Medicare, Social Security, private business bailouts of all kinds, government subsidies of all kinds, etc. At some level, one could argue that something as simple as me attending the free, public dog park in my town or enjoying the free, public library is akin to accepting free money from the government.
I would also ask someone making the "not working is immoral" argument to imagine a hypothetical world in which energy and resources were unlimited. Should one still choose to work in such a world?
That said, even if one does want to make the argument that it's immoral or wrong to "take advantage" of all the programs mentioned, someone in that position should still understand that a UBI is still a better solution than the existing myriad of means-tested programs which can actually discourage work, whereas a UBI doesn't.