Yes Giles gave Xander a scolding but a little thing just like he gave Willow a little remark. That is the thing he is never as harsh as he should be to them but he is willing to let Wood kill Spike. See the double standard? That is why i don't always respect them and never will.
I don't think that's the same. Giles was willing to kill Dawn to save the world, he killed Ben the innocent human to save the world, that's who Giles is. In the original script, Xander was supposed to be Glory's half and Giles was going to kill him to save the world. I repeat "save the world" to emphasize that Giles is a Big Picture man who is willing to do anything to keep the world safe for the billions of people even if it meant killing his child.
When he teamed with Wood to kill Spike, he was doing it because Spike was a ticking bomb. The First declared that it was going to use Spike later and Buffy wasn't doing anything in that regard. In fact, Giles was the only one who was trying to find a way to stop the trigger and get rid of it, but Buffy and Spike weren't helping at all. That's why he joined Wood.
If I was Spike I would have done the same in season 4. He was basically a pet that they sat around and made fun of when he was around. I mean Buffy herself even did that. Being so new into what you are going to have to live like for the rest of your life is hard enough without having people always adding their opinions and insults. So do I think he went about it the wrong way? Yes but I can't blame him for not wanting to join their gang at that point. They want him to be apart of it they should treat him with respect.
I'm going to disagree here. I'm gonna post a quote from an essay I wrote a while back:
"While the Scoobies found it hard to warm up to Spike, Giles and Xander gave Spike a place to stay with free blood. Giles actually let him roam in his place without chains. Xander only chained him when he went to sleep. The decision to move out was clearly Spike's, no one kicked him out.
The Scoobies more often than not ask Spike for help and information later, in which he keeps reminding them that he's evil and that he doesn't like them and that he'd kill them one day when he finds a way to get rid of the chip. The Scoobies still trusted him and considered him on their side. Why would Giles keep blood in his fridge after Spike moved out if he didn't consider Spike one of them? Why would Willow stop Spike from committing suicide? Why would Xander put his life in danger of being hit by falling rocks to save Spike's life? In The Yoko Factor, when Spike planned to 'pretend to go back under disguise into the Initiative', Xander delivered him the clothes appropriate with the 'job'.
The Scoobies got burned for their naivety when Spike started working with Adam, and betrayed that forming trust they had for him.
Xander: Spike's working for Adam?! After all we've done--nah, I can't even act surprised.
Funnily enough, later when Spike asks for forgiveness, Giles and Willow turn their eyes to Xander as if asking his permission to forgive Spike. Xander shrugs and lets him be.
The Scoobies' attitude toward Spike had always been neutral, even Xander and Giles, it was until Buffy told them that Spike is in love with her and appeared grossed by it that Giles and Xander started to be overprotective. Personally, if Buffy returned Spike's feelings by that time, I don't think the Scoobies would have minded having him around, and even Xander will eventually loosen up, he seemed to take it well when he thought that Buffy was sleeping with Spike in S5."