Giles should feel guilty for tricking Buffy into "patrolling" with him when in reality, he was waiting for Wood to make his move on the unsuspecting Spike, whom was arguably her closest friend at the time.
I do agree with you here, he shouldn't have tricked her.
And, let's not forget how Giles didn't seem at all concerned for one minute that Wood might be in danger in his little "attempt" to bring down Spike. Giles only wanted Spike dead and out of the way, regardless of the cost. What was Wood thinking going and purposely triggering Spike's chip? Spike was ten times stronger then him. He was asking to get killed. The only reason Spike didn't kill Wood was because he knew it would upset Buffy. Wood deserved everything that was coming to him.
There's no reason to think that Giles didn't care enough to think about Wood's well-being. Wood would have made it very clear to Giles that he could handle himself, which he must have believed he did. And even if Giles had have tried to dissuade Wood, it wouldn't have mattered. Wood was so determined he would have gone ahead and done it anyway. I don't think Wood deserved everything that was coming to him. He was left without a mother, he was allowed to feel the way he did.
I never said that Buffy made the "right" decision in shutting the door in Giles' face or, for that matter, in giving the heads-up for the removal of Spike's chip. Sometimes Buffy acts with her heart not her brain. Spike WAS a threat, you're absolutely right. He was volatile, unpredictable - you think Buffy cared? She wasn't about to let anything happen to him, regardless. This situation is no different then the situation with Dawn in S5. Buffy wasn't going to allow the chip to kill Spike or hurt him in any way. She did what she felt was necessary. Does it matter if she made the "right" decision? She made it, and it is ultimately her decision.
And so did Giles. You could replace the name Buffy with Giles here and it would also make a very good statement as to why Giles did what he did. He was thinking with his heart, not his head. He also did what he felt was necessary whether it was a mistake to or not. I'm not saying it was his decision, but I don't think it was Buffy's either. Just because she's the Slayer doesn't mean she gets to say who gets hurt, who is a threat, who dies, and expect everyone to go along with it. I do like this point here Joan, it actually made me realise that Buffy really and truly is Giles' slayer/daughter. 🙂