It may well be asked that if God has not created anything without purpose, and everything has been made for the benefit of man, why do some things cause harm, and why were these things not created beneficial without having any harmful aspects? For example, the benefit man and other creatures derive from snakes should have been provided without any harmful side effects. The first answer is that the Creator did what He considered appropriate. We have neither the right nor the ability to criticise the acts of nature. Our job is to find out whether or not whatever is happening in the world is primarily and collectively based on truth, justice, and mercy. When it has been proved that nothing in this world is entirely harmful but has definite benefits hidden in it, and even the things that appear useless and harmful are not really so but appear so because of the lack of our knowledge, then it is most inappropriate to find faults with nature and to ask why something is this way or that way. No wise person can expect that man, who is himself one of the creation, could have such deep insight into the principles of creation that he should be able to tell with certainty the principles underlying the creation of each and everything. So that is my first answer: when something has been established in principle, then it is inappropriate to go on raising random questions, one after another.
Moreover, if we only accept things after all their intricacies have been resolved, then no debate will ever come to an end as such questions would continue to be raised indefinitely. It is only logical that when a thing has been understood in principle, even though some details have yet to be resolved, we should accept it and leave the rest to God.
Now I come to the actual answer. Harmfulness of certain things is expedient in that they sometimes help produce beneficial results. For example, snake venom is used as a remedy in some deadly diseases and, under the law of nature, this beneficial effect is inseparably linked with its poisonous effect. This harmfulness is also beneficial and advantageous in that it helps to indirectly promote moral reformation and material progress. Every wise person will agree with me that occasional hardships and misfortunes are essential for the perfection of man’s morals. One who has never faced hardships and misfortunes in his life cannot achieve perfection of his morals. Similarly, material progress is not possible without such challenges. Therefore, harmfulness in certain things is indirectly conducive to man’s benefit and progress. There must be many more, as yet undiscovered, benefits in it.
One may ask, if these dangerous animals are actually beneficial for man, why are they destroyed and why does religion itself sometimes order us to keep killing them? As a general rule, nature requires a balance in everything, avoiding any gross deviation from the norm. The excess of things with obvious deleterious effects can cause more harm than good. Such things can remain predominantly beneficial if their number does not exceed a certain limit. Therefore, in His ultimate wisdom, God has created these things and at the same time invested man with the tendency, and in certain cases explicitly ordered man, to prevent their excess beyond a certain limit. In this way, the balance of nature has been established.
To summarise, that some things in this world have some harmful aspects is not an objectionable fact. The fact remains that everything in the world is created with a purpose and harmfulness of some things is also indirectly beneficial for man. Therefore, this objection by the atheists is absurd and baseless and only proves their ignorance.