Let's say that Larry makes $100 at his job. He is "taxed" $30 even before he gets his money. (If he manages to get a "refund" from the IRS of all or part of this money, then that amount drops out of the figuring.) Everything he buys is "taxed" so that he actually only gets $50 worth of buying power in exchange for the life he has traded to his employer.
Now, if he gets food stamps and "free" medical services that amount to anything under $50, I can understand how he could be considered to not be stealing from other people. If, on the other hand, he is getting "free stuff" in the amount of $55 I think it's pretty reasonable to say he is stealing (or at least "receiving stolen property") at least $5.
Of course, you also have to consider that the price of everything he buys is grossly inflated due to "taxation" at every step of the way. No one EVER pays "taxes", fees, or any other governmentally-added expense except for the final purchaser. (That's the "consumer"; you and me.) This could give him some extra wiggle room.
So, I no longer really fault those who get some of their own money back- or believe they are doing so. Plus, I suspect that it's all just an accounting trick and every dime of welfare is actually paid with Fed-counterfeited "money" rather than coming from "tax" money stolen from other productive humans.
Now, if you get your paycheck by working directly for "government", then all this goes right out the window. You pay no "taxes"; it is just a game of smoke and mirrors (and more accounting tricks) to give the illusion of you paying. If you do a "tax"-supported "job" that shouldn't be done by "government"*, such as a "public" school teacher, a cop, a DMV drone, military, a licensing bureaucrat, etc. then you are doubly wrong if you get additional "free stuff" from your employer in the form of "welfare".
But, assuming you are doing something that actually needs to be done, and would still need to be done even if no one were coerced to finance it, I don't think your are ethically wrong to take some of your money back from the thief- however much you can get. That doesn't mean it's a good idea or won't hurt you, though.
Remember that there is a grave danger of becoming dependent upon handouts. Think about how you'd react if the handouts suddenly stopped. Or, worse, if you were told they would stop unless you did something you know to be wrong, to appease those who control the handouts. Don't get yourself into that compromised position.
You'd be better off to only use any handouts to undercut The State and its agents in some way. Use the "welfare" to buy silver, bullets, extra food, and things like that rather than the latest computer game or fancy "athletic" shoes. But, it's your life and your choice. Do with this information as you see fit.
*(Notice I am not saying that there would be no similar positions in a free society, but in that case, those who didn't want your "services" wouldn't be forced to pay for them. But obviously, some of those "jobs" couldn't exist in a free society.)
And please don't forget.