Yes, any type of widow spider is poisonous though not to the extent that it can kill you usually unless you have a compromised immune system, are very old, or a small child, baby or similar sized animal. Not enough venom in one bite. Most adults it can make you feel very ill indeed but it won't kill you.
The tiny brown recluse spider is another story. One bite from one of those can ultimately lead to you losing a limb or even death, though that too is pretty rare these days. That happened to a member of my family when he was young and half of his arm went necrotic. He survived but he can't even look at a spider, even a harmless one, he's still so afraid.
They do have anti-venoms and antibiotics now for a lot of the more toxic souders that if you get to the hospital fairly quick they can give you to really minimize the effect of a spider bite, but I understand not for all. I was reading about the spiders in AUS a few weeks ago and apparently the venom from a small few of them actually could just kill you before you can get to a hospital if you happened to be bit in the outback or something.
I've only run into two spiders of the toxic variety, and I hope that's all I ever will. Neither of which got close enough to bite. One was in our fridge salad drawer. It piggybacked in on some new produce apparently. The other was out near our garage. Both black widows. The one in the fridge we just caught in a jar and put back outside. Ditto the one near the garage. We just caught it in a jar and moved it further away from human habitation out in the woods.
I saw no reason to kill them. They were just doing what spiders do, looking for food and/or trying to build a home and spiders are useful creatures, even the toxic ones so I like to leave them alone if I can. I can't have a toxic one near the house breeding though so if I see a widow or something it has to go back out to the nearest woods. Last thing I need around are dozens of them making even more of them, becoming a real threat to me and mine, and I surely would use chemicals to rid someplace of an infestation, but I do try to be fair if it's only one spider.
Spiders don't scare me too much really. I think they are kind of neat actually. That's not to say I appreciate one in my bed, but I can deal with them, most of the time....
Actually the two spiders I met, they didn't freak me nearly as much as the nest of copperheads they found practically right by the front door when I was a kid. As a general rule snakes don't bother me either, but the idea that a whole big pack of young kids were playing in that yard every day for probably months with those things, that's REALLY scary for me to think about even now.
Spiders most of the time you can just walk away.
But poisonous snakes can be aggressive and they move really fast besides.
