Complaint Against Chasidim

תחנון on פסח שני.

In שלחן ערוך, (O.Ch. 131) פסח שני, is not enumerated
as one of the days when תחנון is omitted.

The פרי מגדים explains, "Since פסח שני is a Yom Tov of יחידים (individuals who couldn't make it on the 14th of Nissan)

Similarly, we find the 9 days in the year when individual
Kohanim brought קרבנות (Ta'anis 26a) yet we say תחנון
since it's not the whole Tzibur celebrating, so too on פסח שני
it's not a Yom Tov for the Tzibur, therefore תחנון is to be said".

Many Poskim argue and hold not to say תחנון on פסח שני.
(סידור של"ה אלי' רבה סידור התניא א"א מבוטשאטש ועוד)


In the early days of the מחלוקת between the Chasidim
& Misnagdim the Misnagdim's complaint against Chasidim
was that they don't follow Halacha. One of the examples
they used was that Chasidim don't say תחנון on פסח שני

They didn't complain on the Minhag of not saying תחנון on
a Yahrzeit of a Tzadik. (which is a non-Halachic Minhag )
Since this Chasidic Minhag is exclusively for the Yahrzeits of
צדיקים תלמידי בעל שם. Therefore for the first generation
Chasidim this Minhag hadn't started yet.(Most צדיקים were alive)
Chasidim omitted תחנון only on the days mentioned in שלחן ערוך.
The only complaint re תחנון was on not saying it on פסח שני

It is ironic that today almost all* Yeshivishe & Ashkenaz
Minyanim don't say תחנון on פסח שני.

*Except Chazon Ish & few others