No human being can be insulated from the feeling of being insecure. Simply, afraid of loosing something is so natural to us. As nobody knows what will happen tomorrow, such uncertainty will lead towards a feeling of anxiety and restless. This is a threatening feeling.
I suppose the more that we have, the more we have to lose. What we "have" could be anything including our health, wealth, power, position, family etc. The more we adore things, the more we feel about the impact of the threat. If I could recall what I learned from Maslow hierarchy of needs, once the basic needs are fulfilled, people are looking for higher meaning of life, self actualisation. This could be recognition, respect, support and many others.
When we feel insecure, what would be the natural reaction? Looking inwards should be the logical thing to do as this involves our inner feelings. Understanding ourselves and assessing the "threat" objectively would certainly provides us with the understanding of the root cause of this feeling. However, this may not be that comforting to everybody. Just imagine the wealth that attracts respect towards us are actually obtained from abuse of power or other illegal means? Surely, we will feel very insecure if this become public knowledge.
As a response, many will look outwards and blame other for the insecure feeling that they have. Instead of addressing our inner weakness, blaming others is very convenient. This will make us feel good as it provides us with the feeling that we are not part of the problem.
At the end of the day, we have to live our real lives and endure whatever reality that we face, notwithstanding how people feel about us. It is us that will face the person in the mirror and it is just us who really knows what sort of person that face represents.
So, before we get excited to blame other for whatever insecurity that we may feel, remember that it is our faces that we see in the mirror every morning.