a critique can be if a person say, this must be wrong practice because it is more harmful than good for the one who practice it. (it is a valied critique because the person is concerned about safety and well being)
It depends on how its said. If the person said their belief is wrong as in their theology, it's not an attack but an opinion probably based on that person's personal experience.
Unfortunately, yes, a person's beliefs can be more harmful than good. I don't believe that's based on personal opinion. People have died because of how people express their beliefs.
Its mostly attacking, if one likes, the christian's behavior and attitude because of the latter's theology not his spirituality and personal relationship with his faith.
A attack is when someone call a person evil because they practice a religion that some people only see as evil.
Not to defent my own belief in Islam, but islam as a whole often, but not always has been accused of being an evil path due to terrorists has used it as a shield. And yes of course those who do evil deeds from within a religion are them self evil. but not nessesary the teaching in it self (wrong practice often lead toward evil deeds)
I actually haven't seen any atheist call believers evil... at least not on RF. I have seen christians tell atheist they are wrong, ignorant, blind, and a few are pretty blunt about the eternal damnation of people's souls.
Christian theology does have bad points in. The bible does have a lot of bad points in it-at least from human standards of morality in regards to life and death. Some people learn from it by calling it god's justice.
How to say this... I think you're blinded by what's literally in scriptures because you interpret them from a positive light even if it says otherwise. But in general, no one should attack a person for their belief system but I don't see anything wrong with challenging the validity of their belief or telling them their theology (not their spiritual connection to it) is wrong because of their personal experience with it.
Also, be mindful, many atheists used to be christian. So, they're not unfamiliar with god or god experiences. A lot of people probably do have awakenings just not attributed to god.