Any action that we perform and any decision that we make, even in some simple things like breathing, eating, drinking, walking, talking, opening and closing the door or window, cleaning, washing, or even sleeping, will have certain risks that we might not think of, not to say, for certain people who have certain physical or mental illness, injuries or limitations to be doing something, or for those who have certain allergic reactions towards certain elements in the surrounding environment, objects, sounds, smells, shapes, colours, images, food, drinks, drugs, medications, minerals or chemicals, and etc.
Even with sufficient understanding about our own physical body and mind and its ability and limitation in the present moment, as well as paying maximum attention while performing our yoga practice without forcing the body beyond its limitation, also cannot guarantee that there won't be any physical and mental unpleasantness or adverse reaction during and/or after the practice, not to say, when we have very little understanding about our own physical body and mind and its ability and limitation, or if we don't pay attention onto our practice, or pushing the body to go beyond its limitation, and/or without awareness towards certain risk factors that exist in the surrounding environment.
Some people are not suitable to perform certain yoga practice, while some people are not suitable to perform some of the yoga poses or exercises due to some existing physical and/or mental illness, injuries, or limitations. Not everyone have the same condition of the physical body or the same state of the mind. Even the physically and/or mentally fit people who first try to perform some of the yoga practice or yoga asana practice would also encounter certain unpleasantness or difficulty, and might even develop some adverse reaction during and/or after the practice, not to say, for certain people who are physically and/or mentally unfit, where they might encounter great unpleasantness and adverse reaction during and/or after the practice, which may take some time and regular practice for the body and mind to develop certain degrees of understanding, skill, technique, acceptance, familiarity, patience, tolerance, forbearance, adjustment, adaptation and accommodation towards the practice.
Does that means 'yoga practice', or 'yoga asana practice', or 'certain yoga practice and yoga asana practice' are something 'unsafe' or 'bad' for people, and people shouldn't practice yoga?
Again, it depends on the different states of the mind under the influence of different degrees of ignorance, some minds will think and say, "Yes. That means yoga practice is unsafe and bad for people. It may cause unpleasantness and adverse reaction to our body and mind. We all shouldn't practice yoga," while some minds have different understanding and say, "No. It doesn't. Everything has risk. We take risks at our own responsibility. There are many elements that can influence and minimize/maximize the risks to the minimum or maximum."
There are also many imperfect impure minds within the yoga community whose thinking, action and speech are not perfect, as well as scandalous misconducts existing within the world of yoga. It doesn't mean that 'yoga' or 'the teachings of yoga' is something 'wrong' or 'bad'. Although for those who don't have the basic correct understanding, they would think and say, "Yoga and the teachings of yoga must be so wrong and bad."
If the truth of something is 'nothing good but bad', then everyone who take that thing will all experience 'nothing good but bad reaction', and vice versa. Just like any kinds of drug or medicine might not be perfect or suitable for everyone. Everyone might react towards the same drug or medicine differently. It doesn't mean that the drug or medicine is something good or bad. It is neither good nor bad, but just having its own particular purpose and effect that might work differently on different individuals.
Whether we are aware or unaware of it, most of the time, we all are dealing with many kinds of risk assessment and risk taking while being existing and living in this world.
More importantly, it's about investigating the truth of everything via self-inquiry, measuring what will bring more benefits than harms, be bold and responsible to make any decision or perform any action in everyday life, while taking any potential risks that come along with making those decisions and performing those actions, without fear, blame and regret. It's also everyone's freedom of whether they want to take certain risks, or not.
There's nothing wrong if we don't know much about many things. There's nothing wrong to think and say, "I don't know," or "I'm not sure," as well as be open to inquire the truth towards something that we don't know and aren't sure about. It's better than blind-agreeing/disagreeing, blind-following, blind-practicing and blind-propagating something without thorough investigation towards the truth of it.
Unfortunately, many minds, including some yoga practitioners/teachers, are unaware of themselves are being influenced and conditioned deeply by certain stories, ideas and beliefs to reason and judge everything. While self-inquiry is about freeing the mind from the influence of any particular way of thinking, ideas and beliefs existing in the mind, to allow the mind to see things as it is.