When the Jews spake against it (antilegontōn tōn Ioudaiōn). Genitive absolute again, antilegontōn (antilegō) common verb for speaking against as in Act 13:45. Clementer dicit (Bengel). “The word is a mild one to describe the bitter enmity of the Jews” (Knowling).
I was constrained (ēnagkasthēn). “I was compelled,” first aorist passive indicative of anagkazō, the very word used of Paul’s efforts to get the Christians to blaspheme (Act 26:11) which see. Paul was compelled to appeal to Caesar (See note on Act 25:11, and note on Act 25:12for this phrase), unless Paul was willing to be the victim of Jewish hate when he had done no wrong.
Not that I had aught to accuse my nation of (ouch hōs tou ethnous mou echōn ti katēgorein). This use of hōs with a participle (echōn) is common in Greek for the alleged reason. The genitive case with the infinitive katēgorein is regular. Paul says ethnos instead of laos as in Act 24:17; Act 26:4.