Is it true that Masjid al-Aqsa was built by the Umayyad empire? Should we visit it if we have the chance? Or would visiting it be an insult to the Imams (a)?
Not true at all.
Masjid Al-Aqua existed before the rule of Bani Omayyah and we have in our authentic books authentic Hadeeths from the Prophet Muhammad (SAWA) and Ahlul Bayt (AS) about the great reward of praying in Msdjid Al-Aqsa. ( Kitab al-Mahaasin by Al-Burqi, Kitab al-Faqeeh by Al-Sadouq, Thawab al-A;mahal by Al-Sadouq, al-Orwatul Wothqa by Sayyed Kadhim Al-Yazdi , Kitab Al-Mabsoot by Al-Shaikh Al-Tusi, Kitab Al-Nawaadir by Al-Rawandi, Minhaj Al-Saliheen by Ayatullah Sistani, Tahrir al-Qaseelah by Ayatullah Khomeini and many other books.
Bani Omayyah tried to divert Muslims from Makkah to Masjid Al-Aqsa during their conflict with Abdullah ibn Al-Zubair who was the ruler of Makkah for nine years. Praying in Masjis Al-Aqsa is highly recommended but we should never do any act which can be taken by people as a support for the occupiers of Masjid Al-Aqsa.
Wassalam.