At every spiritual ceremony women, who are in their monthly cycle, are asked, not to touch any temple-items, not to offer flower petals and not to offer anything into a yagna fire. Here is a summary of explanations which Swamiji has given at different occasions, to help everyone to understand why it is like that: Once Swamiji explaining, that a woman is energetically receptive and during the month she collects a lot of negativity from her environment. In doing so she does a great service, as she purifies her environment. This impurities get removed from her during menstruation. At this year´s Bhu Devi yagna Guruji was quite clear, that women in their cycle should not participation in the yagna. He gave the following explanation: “Menstruation is purification. You are going through your personal purification. You should not even touch the person which is performing the puja. You should not even touch other people. When you are doing a ritual everything gets energetically intensified. In menstruation there is already a certain negativity inside. So it gets intensified in the ceremony. So you should keep a certain distance. You can participate with the mind. You see, the manas puja (puja in thoughts) is also very important.”
At another occasion he explained that normally the flow of energy in people is upwards, but during the time of menstruation, the flow of energy in the woman is downwards. In a spiritual ceremony the energy is going strongly upwards towards the Divine. That means, that the flow of energy in a woman is going in the opposite direction than the energy of the ceremony. This causes an energetic disturbance which can lead to not being well. So in telling women to stay at a distance it is also about protecting them from energetic disturbances.
All together, it is not about portraying women as somehow impure. As Swamiji said just recently, women are the physical manifestation of the Divine Mother and menstruation is also given by the Divine for the purpose told above.
With so much explanation for sure it will be more easy to follow this call with a good feeling.