The response that atheists often get from religious and spiritual people: "You need to study religious texts to understand religion" is actually a diversion.
First, there is no one definition of religion and spirituality. Second, even if you studied ten thousand definitions of it all, someone will come along with definition number ten thousand and one when you have your next conversation with a theist or a spiritual person. There will always be something you didn't read or something you missed or something you "don't have a true understanding" of.
That's the game - diversion. They want to send you away on wild goose chases so they don't have to undertake the task of answering your questions. Besides, it's not as if every religious / spiritual person who believes in things like god, karma, afterlife and reincarnation has done all the reading they want you to do. Almost nobody has.
Their beliefs and their worldview don't depend on their studies. They depend on the cultural practices that are handed down to them by their parents and their family. For most believers, acceptance comes first and study of that which they have accepted comes second. They didn't read their scriptures before they decided to start praying. They were taught to pray and later they (perhaps) studied their scriptures as a way to justify the practice of their religion.
This is why their proposal that you'll accept what they believe after you study what they have studied is backwards and at least a little dishonest. It's perfectly okay to base your criticism of religion on the visible behaviour of those who follow religions or call themselves spiritual.
Religious or spiritual practices are, at the end of the day, human behavioural patterns. The effects they have on human beings and the world human beings live in, should be subject to the same scrutiny as any other kind of behaviour that human beings engage in.