Although on the surface I have nothing against hacking, the problem is the people who abuse it, cheat online, and just generally ruin the game for others. The problem is that there isn't really an easy way to police the idiots and leave the sensible people. The outcome is that all hacking has to lead to bans, and is one of the reasons that causes features such as trading or gifting cars get removed, ruining it for the majority who would use these features as designed.
That said, I don't see why online there can't be a database of all the cars in the game with acceptable min and max parameters that is checked whenever someone changes car or joins the track. That way hackers can still make cars and use them offline, but not affect people online. The same check could be applied when trading and gifting.