No. *Some* anarchists are against violence, however, *some* are in favor of violence. The ones who I tend to agree the most with see it as a much more complex thing than merely something to be for/against. It will, of course also depend on how you are defining violence.
As I see it, violence is something that exists. It is particularly prevalent in societies that are hierarchical and based on domination (such as, oh, say... this one), but it also exists to varying extents in all societies, and in the non-humkan world (see dot's answer to the first question I linked to in the comment above for a little more on how we tend not to recognize that). Often times non-anarchists play up the degree of violence anarchists perpetrate, and have often talked about uncivilized nature in terms of being particularly based in violence (the old "red in tooth and claw" thing), though many anarchists (including myself) would argue that the opposite is somewhat more true.
Sometimes anarchists defend violence that is seen as self defense, and will often extend the argument of self defense to attacks on symbols of capitalism, cops, and other things we generally don't like as defensive actions. I have certainly done this at times in my life. I think that is actually a mistake.
Arguments for self defense accept the terrain that power has put forward as legitimate: that violence in defensive action is justified), but I think that always puts us in a reactive position, we are defencding against their attacks and agressions, as opposed to attacking them because we reject them. It also ignores that fact that violece perpetrated by those in power/authority/whatever-we-want-to-call-it will always be seen as legitimate (if it is acknowledged at all), whereas violence against them will always be seen as illegitimate. As liberating as it can be to experience the feeling of transgressing against what is legitimate, I think we need to play on our own terms, not on theirs.
All this is not to imply that I relish violence. I am actually quite wary of those who glamorize violence, and in my personal life try to minimize the amount of violence I engage in because I find it personally distasteful in most situations. Put simply, I'd rather live a life where most of my interactions are based on shared joy and affinity than on conflict. As I pointed out already though, it is impossible to avoid violence altogether and be alive, so determining how and when I encounter violence, to the greatest extent possible is desireable to me.
