If we were to “give a day” to every major Jewish tragedy that occurred in history there would not be enough days. Our wise sages therefore confined the period of national mourning for all tragedies to 3 specific weeks, so we can live normally the rest of the year.
Klal yisroel gave the day of tisha bav to holocaust victims as a day of rememberance/mourning. Yes that day is shared with rememberance of countless other tragedies, but nothing could be more appropriate.
Obviously, the zionists had and continue to have absolutely no interest in or respect for our sages. Their purpose in this case was not even to have you remember the holocaust but to have you remember that the day is brought to you by your friendly hedonistic zionist leaders. Nothing could be more disgusting.