The moral bankruptcy of atheism has been a huge problem with atheistic philosophies since the very first atheist rejected God. However, the "evil God" argument has existed for a long time as well. There is even a website called evilbible.com designed to "spread the vicious truth about the Bible" (i.e. take it wildly out of context to make God seem like a bloodthirsty war criminal who isn't even as merciful as Satan).
For decades, Christians have been able to put these out of context quotes back into context, showing that not only are most of them unbelievably out of context, but even when God's judgments genuinely are as violent as the atheists claim, 1) He took no pleasure in doing it, 2) He had a good reason for doing it in spite of His displeasure, and 3) He has every right to do it. While this approach is fair, and certainly useful for Christians who wonder why such a loving God would do such violent things, it is not quite as powerful as getting to the root of the problem.
In the past, atheists have simply denied that their worldview is morally bankrupt. In the modern day, they are far more open about it. Richard Dawkins, for example, once wrote "The universe that we observe has precisely the properties we should expect if there is, at bottom, no design, no purpose, no evil, no good, nothing but blind, pitiless indifference." (Emphasis mine). And yet, Dawkins is one of the largest proponents of the evil God argument.
Do you see the inconsistency? If evil does not exist, how can God be evil? How can the Bible be evil? It doesn't make sense. Atheists have a variety of ways of getting around this, but all of them utterly fail to prove morality exists. Not only that, but these atheists already deny that evil exists. The argument, therefore, is more about "I don't like the Bible" than "the Bible is objectively evil".
But the thing is, you're not supposed to like the Bible. The Bible has many purposes, only some of which is to comfort us. It is more than just a love letter. It is also a court summons designed to inform you that you are being placed on trial, and you will be charged, found guilty and sentenced, unless you happen to have the world's greatest lawyer (Jesus) to plead your case. It is a command to rebels, such as ourselves, to surrender to our rightful king, lest we face charges of treason and face the death penalty. It is a record of past executions, designed to show us exactly what our Lord must do to those who rebel against Him. You're not supposed to like that, for the same reason a criminal is not supposed to like it when a police officer shows up at his house with a set of hand cuffs.
The ultimate problem here is that the evil Bible argument is circular reasoning. If the Bible is true, God cannot be evil by definition. Therefore, you cannot use the "evil" in the Bible as an argument against it because that assumes it is not true in the first place. Atheists are supposed to hate circular reasoning, and yet such a circular argument as the evil God argument is so commonly found in their arsenal that virtually every apologetics website has a counter argument locked and loaded. It's simple: If atheism is true, there is no evil, and thus God is not evil. If Christianity is true, atheism itself is evil, whereas God cannot be. Thus, there are no logical scenarios in which the evil Bible argument would work. I certainly wouldn't want to be an atheist if this is the best they have.