Whatever motives Boris Johnson had for calling them letterboxes does not remove the fact that some men have made face covering an 'Islamic' obligation when it is not one.
The face veil removes the humanity from women.
When challenged over the Qur'anic ruling on this, those that cover up are remaining silent or throw up nonsense like 'Islamophobic'.
As for their right to wear what they want, try telling that to their husbands, fathers, brothers or local god called mulla, who make them wear this or else! There is no freedom of choice when you are told a dehumanising face covering is a Sunnah, an obligation and to deny the sunnah is to deny the Messenger, which in turn denies Allah, hence apostasy and we all know what this means in their barbaric, distorted version that I will not grace with the term 'Islamic' but call Bukharian idolatry.
This is what they are reading, where Umar is described as a peeping tom, looking at women going about their bodily functions:
Volume 1, Book 4, Number 148: Narrated 'Aisha:
The wives of the Prophet used to go to Al-Manasi, a vast open place (near Baqia at Medina) to answer the call of nature at night. 'Umar used to say to the Prophet "Let your wives be veiled," but Allah's Apostle did not do so. One night Sauda bint Zam'a the wife of the Prophet went out at 'Isha' time and she was a tall lady. 'Umar addressed her and said, "I have recognised you, O Sauda." He said so, as he desired eagerly that the verses of Al-Hijab (the observing of veils by the Muslim women) may be revealed. So Allah revealed the verses of "Al-Hijab" (A complete body cover excluding the eyes).
Where are the complete body covering except eyes, Al-Hijab verses of the Qur'an? Here is one:
17:45 When you recite the Qur’an, We put an invisible veil (hijabun)between you and those who disbelieve in the Hereafter. [17:41. Disbelievers in the eternal life remain preoccupied with the glitter of this world, a mental barrier to understanding]
17:46 And We (Our Laws) place shields over their hearts and minds to prevent them from grasping it, and cause deafness in their ears. Their minds, hearts, and ears act impermeable when you mention your Lord in the Qur’an; Him alone, they turn their backs in disgust. [They wish to hear about other deities and false ‘authorities’]