I've not encountered anyone who has an interest in attacking religious belief simply because they consider it irrational or baseless; many beliefs retain such elements. It's because religious belief has traditionally primarily adopted the role of the basis of an openly hierarchical institution (the Roman Catholic inquisition, excessively theocratic Islamic states today, etc.), or the basis of other negative influences that have the effect of causing intrusions into non-religious elements of life, as noted by the cartoon, that there is opposition.
It's a sad thing to say but there have been more people killed on planet Earth in the name of God than for any other reason.
That is a totally false statement.
Tens of millions of people were killed in both WWI and WWII. And it had zero to do with religion.
Also, tens of millions of people were killed and murdered during both the Russian and Chineese communist revolutions and subsequent takeovers.
And again, it had zero to do with religion, because the revolutions were led by secular atheists.