Let me tell you why Podolski is not getting hate while Giroud and Walcott are, without bashing on the latter two.
Firstly, Podolski was never hyped up to be as world class as Giroud was hyped by Arsene, and if you look through the interviews given by Wenger, you can see that Wenger stayed very loyal to Giroud. Higher expectations yield higher disappointment. Moreover, Podolski was sold to make room after only two seasons during which we were rebuilding, and when the title challenge wasn't really on the plate or being discussed. Podolski was a plan B in case Van Persie left, and for what we needed him, he was great.
Since then, we acquired Mesut Ozil, Alexis Sanchez, Petr Cech - all accomplished players with aspirations and achievements on the top level. We've won two FA cups, the title challenge is back on, which we want to win for players like Rosicky who endured with the club for so long - in a way for the club and fans to thank and remember Tomas.
Let's be completely honest with ourselves - the league was ours to lose in January, and we fucked it up. Giroud failed to score in 19 of the last 20 games. Walcott plays like a scared dog and Coquelin's flaws started to show without Cazorla. Is it their fault? Who knows. Maybe its the manager, maybe the team became toxic, or maybe its the players' fault - we will never know, it's easy to point fingers and its easier to make someone a scapegoat when your expectations suddenly collapse.
Now secondly, and probably more importantly, Podolski loves Arsenal and the fans, which seemed very genuine and the fans never felt that he was just happily collecting money from the club even though his wages were around 100k per week. Poldi didn't score many goals, but man when he scored it was fantastic. Thunderbolt of a foot.