Ashamed? how very mundane! At this point in time, with the degeneration in the teachings and behaviours of monks and their leaders, even non-Buddhists are ashamed.
As already said, Buddhists have no reason to be ashamed, and countless reasons to be proud, of their Dharma, which is only pure and beneficial in the beginning, middle, and end.
Also, many non-Buddhists have plenty of reasons to be ashamed, not of Buddhism, but of the atrocities instigated by their own scriptures, such as the Torah, the Bible, and the Koran.
Besides, pseudo-Buddhists, such as Dalaites, the followers of the perverse instructions of their wicked cult-leader, the evil dalai, should be ashamed of their grotesque witch-hunting ideology.
But hold not your breath. The very nature of evil doers is shamelessness. And being shameless, they try to induce others into feeling ashamed of that which is only pure and beneficial.
Therefore, expect a lot of propaganda about “how much Buddhists should be ashamed of themselves”, but hardly any comment about how much, for instance, Jews should feel ashamed that their Jewish racist state dropped 21,000 metric tons of forbidden explosives on the heads of innocent Palestinian women and children only in July-August 2014.
While the names of 1614 fatal victims names have been confirmed - the actual death toll, according to the Palestinian Ministry of Health, is at least at 2,137, including 578 children, 264 women, and 103 elderly, while more than 11,100, including 3,374 children, 2,088 women and 410 elderly, have been injured (
http://www.imemc.org/article/68429).
Everything, of course, with the shameless accomplicity of many US taxpayers.
Therefore, in order to distract people's attention from such unspeakable crimes, there will always be someone spreading the poison that “Buddhists should be ashamed of themselves”. You have obviously allowed yourself to be inoculated by this poison.
In order to help people better to direct one's sense of shame, here follow some images of what is indeed suitable being ashamed of -- not Buddhism: