Because whether Silva would work for/with an organization like SPECTRE is based around what kind of organization SPECTRE is. Are you being serious?
We don't know much about what kind of organization SPECTRE is, or how they interacted with Silva. We know about one meeting, and what happened in one scenario.
Silva's demenor, attitude and mental unhingedness would make him an odd choice for a group like SPECTRE. SPECTRE wouldn't hire "wild cards". Not ones who might kill Blofeld's own prey.
What are you basing this on?
SPECTRE shows that in fact, SPECTRE did work with said "wild card".
Silva is a merc. That is how he is portrayed. That is why he says missions.
And...
Very simple. These are the ones who handle high value targets. Remember, they specifically need to pick someone else before they try and kill the Pale King again.
They don't just send random goons after such targets. At the beginning of the movie Sciarra is personally handling a bombing. In Casino Royale, Mr. White is personally handling the situation with LeChiffe and the terrorist.
Bond is the highest value target of them all. Why would Silva be allowed to kill him if he is working with or for SPECTRE?
Because as I pointed out, they may have wanted Bond dead or out of the way at the time.
His entire conversation with Bond in Skyfall says he does.
Nope. Nothing in Silva's conversation with Bond suggests that there are no restrictions. He says he chooses his own missions, and implies that it's easy to accomplish things.
By the way, choosing his own missions does not imply any restrictions, when SPECTRE shows there would clearly be some. This includes kill Bond, which he almost does a good 5 times in Skyfall.
And again, maybe SPECTRE wanted Bond dead at that point in time. Seeing as how the people with Vesper try to kill Bond, and the agents in QUANTUM try to kill Bond, that would seem to be the case. Maybe Blofeld came up with his fancy torture plan later on.
If Silva is working with SPECTRE, why would he be allowed to Kill James? Blofeld said he was waiting for him. He clearly wanted to reveal his great torture plane to him. So Silva kills him randomly. How does Blofeld exactly do that now?
He doesn't. If Silva wanted to kill Bond, do you think he'd let someone tell him not to?
James. Bond. Blofeld. Plan.
Blofeld never says that, over all that time, his goal was to keep James alive so he could torture him later. He says he is the author of all James' pain. He never says that's the only thing he does. When he HAS James, he tells James he wants to torture him and then kill him. That's after he has captured Bond.
The internal logic of Skyfall and SPECTRE don't match up if Blofeld is so willing to let Silva kill Bond.
Again, that assumes the standing order on Bond wasn't just "capture or kill". Or perhaps "capture, turn into an asset or kill".
The meaning of them certainly changes, which is what people are mentioning is a problem and you are ignoring. It also doesn't line up with the internal logic of Skyfall and SPECTRE.
If anything, the meaning of Silva's actions now has more layers to them.
The personal meanings of Silva's actions are not suddenly erased because causing Bond pain is also involved.
The only major thing that changes is that Silva will have been works with/for someone, which is one of the less important aspects of his character anyway, seeing as how it is given so little time. I believe there's a line or two of dialogue about it. Most of the Silva's character focus is on his disillusionment with MI6. That hasn't changed.
