Yeah, he's definitely had a rough go of it for sure, and really didn't seem to grow up in an environment that would prepare him to have his crap together at 23 years old. I think the issue with him right now is that we don't really know the details of most of this stuff, so it's unclear if his behavior are things we can explain AND excuse, or if his behavior is things we can explain and CAN'T excuse.
For instance:
Weed in Alabama: If you're in a state with really draconian weed possession laws it's dumb to be carrying weed around, but this is something I can both explain and excuse.
The Gun: Is it a gun he bought legally in a different state that's illegal in the state of CA and he didn't know that? Again that's dumb, but I can explain him making bad decisions, and can excuse him doing something dumb. Or maybe it's a federally banned gun with no serial number on it that he bought off someone? That I can explain but can't really excuse, and as it's a federal crime he's probably going to serve jail time for it. IMO there could be a big difference between "explain" and "excuse" on this one, depending on the details.
The Altercation: We know he was living with his long-term girlfriend, they got in a fight, and he was kicking her out -- he put her stuff on the porch. The accusation is that he also dragged her out of the house, which is where the DV charge comes from. Did he carry her out of the house? Did he pull her by her shoulders out of the house? From his background I can explain him having an unstable relationship with a SO, and I from that explanation I can excuse those types of things, thinking he probably needs to get out of that relationship and needs to get some counseling. Or maybe he dragged her out by her hair, or literally tossed her out of the house, or struck her with an open or closed fist or choked her while dragging her out of the house. I can explain that too, but can't excuse it at all. IMO there could be a HUGE difference between "explain" and "excuse" on this one, depending on the details.
9ers fans are comparing Foster to Aldon Smith, but I don't really think that's right. Aldon has addiction problems and was a huge dumbass many times over, but never hurt anyone. Foster isn't close (yet) to Aldon's many, many instances of dumbassery, but he may have hurt someone.