You mean with those who support the Tusk government.
PSL, as you may well remember, was in the government with SLD, PO and even PiS (on local government/municipal level).
That's real politics. The point is to have real influence on those in power - if you can't win the elections then at least as a coalition partner. This way you can keep and develop your political structures, make sure that your aims are - at least partially - realised, and you can block the most idiotic ideas of your coalition partners if such need arises.
Of course, you can - as Konfederacja does - stay outside and only criticise everything; a very comfortable position but ultimately pointless.
You stand against Poland's interest
Believe it or not (they probably don't write it in "Najwyższy CZAS!") but PSL is consistently most pro-Polish party. They are not exceedingly either pro-American, pro-Russian or pro-European, they look first for the interest of Poland in the long run. Peasant common sense. Salt of the Earth.
ah, but maybe you have an interest of your own
I have children.
Their future is my interest, and their future depends on whether Poland is a safe and prosperous country. I don't feel like emigrating and selling my heart and heritage for a couple of dollars/euros, so I stand with Poland through thick and thin like PSL always have...

from now on I'm holding you personally responsible for everything the government does and doesn't do
0_0
You
greatly overestimate my political influence.