I've got some good news for you
J G Tasan :) You don't have to feel guilty or even "lukewarm" in your endorsement of a prayer petition
"For our (anti-Christian, blaspheming)
bretheren who are celebrating (whatever anti-Christian, blaspheming holiday)."
It's all a matter of understanding the nature of the petition itself. Technically, they
are our bretheren. All people are "brothers" in that we are all fellow children of God and His handiwork. That remains true
in spite of their obstinate refusal to follow God's one true Faith within His One True Church. So the term "bretheren" is accurate.
It's a meritorious act of Christian charity to pray for unbelievers. Christ Himself prayed for his persecutors, even while hanging from the cross in unimaginable agony.
As Catholics, we can and probably even
should pray that God treat today's unbelievers mercifully and grant them the grace to open their hearts to His Son Jesus and His Church. All the moreso when they're celebrating some foul anti-Christian parody of a "holiday" (a word deriving from the term
holy day).
The important difference is that praying FOR a sinner does not imply that we should condone the sin they commit, which is
exactly what modernist hippy-dippy ecumenical clergy would like us to do.
I'll give you an even tougher example... praying "for the intentions of the supreme Pontiff" in a group rosary. Oh dear...
:PI personally know of a pastor who felt compelled to explain why it is still licit for devout Catholics to pray for "intentions of the supreme Pontiff" aka (the intentions of the Holy Father).
The pastor pointed out that
the intentions themselves, are all quite laudable. How certain agencies within the Vatican would apply those intentions to the world and The Church is an entirely different matter.
He drew a further distinction between praying for Pope Francis'
published intentions and whatever
personal intentions the man might have, either for the world or The Church.
Apparently much of the pastor's flock were bleating rather nervously at the idea of praying to God for
anything Pope Francis might intend, as well they should.
;-)