I think I want to tell a story. Okay, I know, I tell stories sometimes.
So, I played as a kid and loved TT. But I did not really play. It was recreational TT. I loved it. I was addicted to it. But I had no idea there could be a forum for playing TT with people who really played TT. I played when there was a table and someone willing to play with me.
The sport I really played as a kid was baseball. I played baseball from age 4 straight through high school and I played every year, starting months before the baseball season started, despite it being kind of cold out, and played as late into November or December as possible....till the cold temperature forced me and my friends to switch to playing football.
As a teenager, in the summers there was a Tennis club my father played at that had a table and I used to go and play TT with the Tennis kids from the tennis club. Some of them are still friends of mine 40+ years later. They played TT as though it was Tennis. They would laugh at me when I tried to play tennis and told me I played Tennis as though I was playing TT.
The point of this is, we played all TOPSPIN, no deception, blasting the ball and the player who could overpower the other was the player who would win. No backspin serves. No pushing. All topspin. One summer, I played all summer. Every day I could. As much as I could. When I came back from summer vacation and played in my little league baseball team, NOBODY could strike me out. Nobody. I am sure it had a lot to do with playing TT all summer. But it was only topspin attacking shots.
In my late 20s between jobs, I found a real TT club. Amazing. In my mind it was the best club I have ever seen. It is still larger than life. I joined. While I was off work I played every day for about 3 months. They had a robot. I improved my strokes with the robot. But I could not beat any of the players from the club because I had no idea how to handle backspin. I had never faced real backspin. Or deception on serves.
Then I did not play again from when I was 27 till I was 44 years old. At the time, as a yoga teacher, there were only a few things that still really got under my skin and got me angry. The big ones were my wife. And boy she knew how to get under my skin. And my parents. Not much else would really get me into a deep unshakable anger, rage.
And then I saw these TT tables near one of the studios I was teaching at. This was outdoor tables at Bryant Park NYC. One day I decided to jump in and try. I had not played in 17 years. Now, at that point in my life, I probably would not have gotten hooked back in to TT if there had not been something. And there was.
So I was playing all these guys who did cheap defensive stuff. They just chopped or pushed and hoped you missed. They were playing hoping you would lose the point rather than trying to win the points. And at the time it made me enraged that I would lose to these guys I was sure I was better than.
And, for me, that was actually the hook. I realized this was the perfect opportunity for me to watch what actually gets me angry and under my skin and to use it to see if I could figure that out better. For me, it was the feeling of not being in control. Having the ball go into the net without me knowing why or what to do to change it.
Now the interesting thing for me was, when I realized the issue for me was control, it made it so there were a lot fewer things that got me mad outside of TT. For years, my parents no longer got me mad. These days, my mom can get me mad again because she can't freakin' hear and refuses to accept that she can't hear.

But it is not a big deal.
I never did get it so my wife stopped being able to push my buttons. But I got it so I responded a lot less to it and did not let it get out of hand. Well, when she had cancer and I knew there was only one way things would go, then she couldn't get me angry any more. But not till then.
And for me, the big thing that helped me with getting upset in TT with these guys who were beating me with cheapo defensive play, pips or crapy illegal serves was, I realized that, in some way they were actually better than me and that, the thing to do, if that was the case, was work on my TT skills so that those things did not mess me up any more.
The first step is to acknowledge that they are actually better than you (at least in some sense). The next step is to take the steps to improve so that these players cannot take advantage of those weaknesses because they are no longer weaknesses.
All good players deal with borderline, questionable or downright illegal serves. Good players learn how to handle returning them.
These things should not make you upset. They should make you want to improve your skills so you can get the best revenge on those guys with the questionable serves: you return them and beat them. That will only happen if you do the work and stop blaming things outside of your control.